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A multiple-site perineal applicator (MUPIT) for treatment of prostatic, anorectal, and gynecologic malignancies
Ina. 1. Rodiarion Oncology Biol. Phys., Vol. Printed in the U.S.A. All righls reserved.
10,
pp.
297-305 Copyright
C
0360s3016/84 1984 Pergamoo
53.00 + .M) Press Ltd.
??Technical Innovations and Notes A MULTIPLESITE PERINEAL APPLICATOR (MUPIT) FOR TREATMENT OF PROSTATIC, ANORECTAL, AND GYNECOLOGIC MALIGNANCIES ALVARO MARTINEZ, M.D.,‘T~ RICHARD S. Cox, PH.D.2 AND GREGORY K. EDMUNDSON’ ‘Presently from the Department of Oncology, Division of Therapeutic Radiology, Mayo Clinic, Rochester, MN 55905; 2 Department of Radiology, Division of Therapeutic Radiology, Stanford University School of Medicine, Stanford, CA 94305 Recently, transperiwal interstiti&intracevitary applicators have been used to treat IoeaIly limited and advanced perineal and gyneeologic malignancies. We have developed a single afterloading applicator, referred to as the “MUPIT” (Martinez Universal Perineal Interstitial Template), whlcb with its prototypes has been utilized to treat 78 patients with malignancies of the cervix, vagina, female uretbra, perineum, prostate, and anorectal region. The device baslcally consists of two acrylic cylinders, an acrylic template with a predrilled array of holes that serve as guides for trocars, and a cover plate. Some of the guide holes on the template are angled outward to permit a wide lateral coverage without danger of striking the ischlmn. The cylinders have an axial hole large enough to pass a central tandem or a suction tube for the drainage of secretions. Thus, the device allows for the interstitial placement of ‘uIr ribbolrs as well as the intracavitary placement of either ‘uCs tubes or % ribbons. In use, the cylinders are placed in the vagina and rectum and then fastened to the template, so that a fixed geometric relationship among the tumor volume, normal structures, and source placement ls preserved throughout the course of the implantation. Hollow, closed+uul, stainless steel trocars are then inserted through the guide holes that produce optimal coverage of the treatment volume. Appropriate computer programs also have heen developed on a minicomputert for the corresponding dose-rate computations. These programs run with suillcient speed that they may be used for both the planning of the source placement beforehand and the computation of the actual dose-rate distribution obtained. The advantages of tbe system are (1) greater control of the placement of sources relative to the tumor volume and critical structures owing to the fixed geometry provided by the template and cylinders, and (2) improved dose-rate distributions obtained by means of computer-assisted optimization of the source placement and strength during the planning phase. Perineal interstitial applicator, Prostate, Anorectal, Gynecologic tumors.
INTRODUCTION
produce a more homogeneous distribution of radiation dose. The Syed-Neblett parametrial butterAyS and the Syed-Neblett rectal templateI were developed to treat single-site tumors. At the same time, but independently, we were working with a multiple-site single-template interstitial-intracavitary applicator, the MUPIT (Martinez Universal Perineal Interstitial Template), which provides for the use of both 13’Cs tubes and i9*Ir ribbons. In conjunction with external-beam irradiation, the MUPIT (and its prototypes) has been employed in the treatment of 78 patients with primary or recurrent cervical, vaginal, female urethral, perineal, prostatic, and anorectal carcinomas. This report focuses on the description and use of the MUPIT, which provides
Locally advanced perineal and gynecologic malignancies are often difficult to manage by either radical surgery or conventional radiotherapy and present a therapeutic challenge. Presently available intracavitary applicators, such as the Fletcher-Suit,13 the Henschke,’ the Bleodorm3 the Delclos,4 the Chassagne,’ and others, have been effective in controlling early gynecologic cancers, but the local control rates for advanced disease remain ~ow.‘*~~‘~~-~* The most likely explanations are inadequate tumor coverage and tumor-dose inhomogeneity within the implanted volume. The transperineal interstitial-intracavitary applicators are intended to improve target-volume coverage and to
Clinic, for their contributions to the construction of this applicator. Our gratitude to Ms. June M. Henn for her secretarial assistance in the preparation of this manuscript. tPDP 11/SO. Accepted for publication 23 September 1983.
Reprint requests to: Alvaro Martinez, M.D., Division of Therapeutic Radiology, Mayo Clinic, Rochester, MN 55905. Acknowledgements-We thank Mr. Peter Hausman, machine shop of the Stanford Radiotherapy Division, and Mr. Warren N. Lenz, Section of Engineering, from the Mayo 297
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February 1984. Volume IO. Number 2
(1) greater control over the placement of sources relative to the tumor volume and critical anatomic structures than is possible with other applicators and (2) improved dose-rate distributions by utilizing computerized optimization of source placement and source strength during both the planning and the loading phase.
DESCRIPTION OF THE APPLICATOR The MUPIT consists of a flat acrylic template and a flat acrylic cover plate, two sets of acrylic cylinders, obturators, screws, and stainless-steel needles of different lengths (Fig. 1). The template and the cover plate each measure 11 cm vertically, 8 cm horizontally, and 1 cm in thickness. In use, the vertical axis of the template lies roughly along the anteroposterior direction in the patient and the horizontal axis along the lateral direction. To avoid confusion, the terms “inferior” and “superior” will be used, with their customary meanings, when referring to the patient, and the terms “upper” and “lower” will be used when referring to the vertical directions of the template. The template has an array of holes that, for the most part, determine the geometry of source placement with respect to anatomic structures (see Figs. 7 and 12). Three large holes are located along the vertical centerline: the top slotted hole allows the passage of a Foley catheter from the urethra and the center and bottom holes accommodate the vaginal and rectal cylinders, respectively (Fig. 1). To allow for differences in anatomy, the cylinders of each set have two diameters; however, they all have flanges that are well matched to their corresponding holes in the template. Once the appropriate-sized cylinders have been inserted into the patient, the template can be bolted firmly to the cylinders (Fig. 2), thereby fixing the geometric relationship of the template and the anatomic structures. To further fix the geometry, two small holes (located in each corner of the template) are used to suture the assembly to the patient’s perineum. Around the three large holes in the template is a bilaterally symmetric array of small holes that serve as guides for trocars (Fig. 1). The interstitial capability of the MUPIT is utilized by transperineally inserting the trocars through the guide holes and afterloading them with ‘921rseeds. The layout of the guide holes is such that the inserted trocars lie in parallel horizontal planes, perpendicular to the plane of the template (Fig. 3). These planes are spaced vertically at about 1 cm intervals; the actual spacings were determined so as to provide a regular distribution about the large holes. To achieve this geometry, the array is made up of horizontal rows of holes that are of two types: type I rows, wherein the holes are perpendicular to the template (Figs. 3 and 8) interspersed with type II rows, wherein the holes are oblique to the template, angled approximately 13” lat-
Fig. 1. MUPIT contains acrylic predrilled template and cover plate, acrylic cylinders, obturators, screws, and stainless steel needles.
Fig. 2. Acrylic predrilled template attached to both the rectal and vaginal cylinders. Obturator of one of the two cylinders is not used.
erally outward (Figs. 3 and 13). The use of the type II rows allows a wider volume of parametrial or pararectal tissues to be covered at depth without danger of striking the ischium. The holes in each row are spaced 12.5 mm apart. Thus, a volume extending 4cm to either side of midplane can be covered by the use of only type I rows. When type II rows are added, volumes extending laterally outward to 7 cm can be covered at a depth of 14cm. The vaginal and rectal cylinders provide the intracavitary capability of the MUPIT (Fig. 2). A center tube runs the length of each cylinder and is designed to accept either the tandem for 13’Cstubes or a drainage tube. In addition to having a center tube, each cylinder has a flange that carries an array of eight guide holes for the placement of trocars. The guide holes are located on a circle that is slightly smaller than the diameter of the cylinder. and they continue as grooves along the length of the cylinder. This design facilitates the placement of trocars near the vaginal or rectal wall.
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cylinders of the appropriate diameter and length are chosen. The lateral, anterior, and posterior extents of the treatment volume are determined, and the corresponding lateral, upper, and lower guide holes in the template are selected. The superior extension of the tumor determines the depth to which the trocars must be placed, and the inferior extent determines the number of sources per ribbon required for adequate coverage of the treatment volume. These data (the identification of cylinders and guide holes utilized, the depth of insertion of the trocars and tandem, and the number of sources per ribbon) serve as input for the treatment-planning computer program. Since the geometric relationship of the cylinders and trocars is fixed, the three-dimensional positions of all the individual seeds and tubes can be calculated. Dose rates at any point can then be determined by furnishing the activity of the sources chosen from the current inventory. Distributions of dose rate are computed in crosssectional planes (parallel to the template) at depths specified by the user, usually every few centimeters throughout the treatment volume. If the dose-rate distribution is judged to be inadequate, modifications are made in the plan and the distribution is recalculated. Once a plan is accepted, the physician knows exactly what protocol to follow in the operating room and what the resulting dose-rate distribution will be, since the geometry is completely fixed by the applicator. If the chosen plan cannot be executed in the operating room, further planning is required between the time of placement and that of afterloading. with two rows of straight needles on the right and three rows of straight needles and one row of angled needles on the left. Different lengths on each side. Fig. 3. MUPIT
IMPLANTATION
PROCEDURE
Patient preparation
are modified 17-gauge needles that have a bore large enough to accept the ig21rribbons (Fig. 3). The pointed end is sealed with a small fillet of solder and reground to resemble the point of a nail. The opposite end is flared to facilitate loading (Fig. 3). To cover treatment volumes that may vary widely in depth from patient to patient, several sets of trocars of different lengths are available. The trocars
PREIMPLANT
PLANNING
The patient is seen conjointly at the subspecialty clinic corresponding to the site of origin of the tumor. When the patient becomes a candidate for primary radiotherapy, a complete workup is obtained and the need for external-beam therapy, in addition to the implant, is assessed. Most patients are treated with a combination of external-beam megavoltage irradiation and the MUPIT implant. A discussion of the integration of these two modalities is a subject of another publication. The type of anesthesia is selected, and the factors involved in treatment planning are determined. Vaginal and rectal
After the planning session has been completed, the implant procedure is scheduled. For bowel preparation, the patient is advised to take clear liquids the day before admission and is hospitalized 24 hr before the implantation. Preoperative laboratory studies include complete blood count with differential platelet count, coagulation studies, electrolytes, urinalysis, chest roentgenogram, and electrocardiogram. If the patient is well hydrated and in good general condition, one bottle of magnesium citrate is given the morning of admission. One gram of neomycin every 4 hr and 1 g of erythromycin every 6 hr are administered orally. Tap water enemas are given until the return is clear; these are followed by a retention enema consisting of 0.1% neomycin in 500 ml of normal saline, followed again by tap water enemas until the return is clear. The enemas are usually completed by 4: 00 p.m. on the evening before implantation. The perineum is shaved. Female patients also receive two vaginal douches with povidone-iodine. On the morning of implantation, thigh hoses are fitted and fluids are started intravenously. Potassium replacement is added, if indicated. In the operating room, a
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pelvic examination with an anosigmoidoscope or a cystoscope is performed when required with the patient under general anesthesia. The extent of the tumor is carefully reassessed, and radiopaque markers delineating the tumor margins are placed. Cervix and vaginal implantation. The patient is placed in the lithotomy position and several 1-O silk sutures are stitched through the normal tissues (whenever possible) or tumor (or both). By applying gentle traction on these sutures, the tumor can be immobilized during insertion of the trocar. A Foley catheter with diatrizoate in the balloon is left in the bladder. If necessary, the cervix is dilated, the uterine canal is sounded, and a tandem is inserted. The sutures are pulled through the central orifice of the vaginal cylinder, and the cylinder is slipped over the tandem into the vagina and fixed to each other with a set screw. The template is then attached to the cylinder and sutured to the patient’s perineum; special care is taken to avoid tilting the template. The physician, utilizing a double glove, places a finger in the rectum. While the assistant pulls gently on the sutures, he pushes the first needle transperineally through the tissues to the appropriate depth. Next, the needles nearest the rectum are then inserted while gentle tension is maintained on the sutures. Care is taken to avoid either perforating the rectal mucosa or leaving the free-floating needles in the rectal lumen. After the surgeon’s finger is removed from the rectum, the cylinder is placed in the rectum and attached to the template. This assures that a fixed distance between the vaginal and the rectal canal is maintained and that the posterior rectal wall is held away from the radioactive sources. A rectal tube is inserted for removal of flatus and drainage of secretions. The remaining needles are placed around the vaginal cylinder to the preset depth. The sutures are removed. The template is sutured to the perineum with 1-O silk sutures, and the cover plate is placed over the sutured template and screwed to it to prevent displacement of the needles (Fig. 4). Sterile gauze is placed between the skin and the template (Fig. 5). The Foley catheter is attached to the draining bag. Care must be taken to keep the bladder distended so as to decrease the radiation to this organ and to displace the small bowel away from the sources of radiation. The rectal tube is connected to intermittent suction. Rectal implantation In the operating room, the patient is placed in the knee-chest position and a Foley catheter is inserted. The preselected rectal cylinder is inserted and fixed to the template. The template is sutured to the skin with silk sutures. The needles are then inserted transperineally to the preset depth. When the lesion is in the anterior anorectal wall, in males, care must be taken to avoid perforating the prostatic urethra. In females, the vaginal cylinder is utilized to keep a fixed distance between the rectal and vaginal walls. A rectal tube, applied to
February 1984. Volume 10, Number 2
intermittent suction, is inserted through the center hole of the cylinder. Generous gauze padding is utilized to cover the template. Prostate implantation After the staging pelvic lymphadenectomy is completed, the endopelvic fascia is opened and the prostate gland, seminal vesicles, and posterolateral pelvic wall are exposed. Metal markers are placed to delineate the boundary of the tumor. With *the patient in the lithotomy position and the surgeon’s one hand in the peritoneal cavity, the guide needle is positioned transperineally just below the pubic bone and pushed into the peritoneal cavity, until a satisfactory superior margin is obtained. This needle is then removed, and the depth of the insertion is measured so the correct needle length can be determined. The template, “upside down,” is applied against the perineum. Utilizing the previous skin puncture and needle tract, the most superior needle is inserted to the preset depth. The remainder of the needles are -
Fig. 4. MUPIT sutured to patient’s perineum. Foley catheter, cylinders, and needles in place. The funnel-like configuration on the end of each needle facilitates afterloading. The cover plate is screwed to the template to keep the needles and
radioactive material in place.
Multiple site perineal applicator ??A. MARTINEZer al.
301
Complated MUPIT implant in a patient with Stage IIIB cancer of the cervix.
Fig. 5.
then positioned transperineally; however, the spacing of the tips is checked intraperitoneally. Rectal examination is performed to be sure that no needles have penetrated the rectal mucosa. The rectal cylinder is inserted, and a rectal tube is secured to the skin and connected to intermittent suction. The template is sutured to the skin with 1-O silk sutures and the cover plate is screwed to the template. The abdominal skin is closed (Fig. 6). A Foley catheter with bladder distention is maintained until the MUPIT is removed. Female urethral implantation
Although the patient is hospitalized the afternoon before the procedure, a less extensive bowel preparation is ordered. In the operating room, with the patient in the lithotomy position, several silk sutures are stitched through the tumor in order to immobilize the tumor during insertion of the needles. A three-way Foley catheter, 14-F to 16-F, is selected. Methylene blue is injected into the third lumen, and a small hole is made in the catheter. A trocar with a blind end is introduced through this hole into the Foley catheter and is advanced
Fig. 6. MUPIT implant with the template “upside down” in a patient with Stage C cancer of the prostate. Note the funnel-like configuration of needles. Cover plate not yet placed.
to the base of the balloon. This will allow afterloading of “*Ir inside the urethra. The tip of the catheter is passed through the plate hole and inserted into the urethra. The balloon is filled with 5 ml of diatrizoate, and the bladder is drained. The template is sutured to the perineum, and the periurethral needles are inserted to the preset depth. The vaginal cylinder is introduced to increase the stability of the applicator, to allow implantation of the anterior vaginal wall, and to displace the posterior vaginal wall away from the sources. Gauze padding is utilized around the template, and the entire applicator is covered. Postoperative procedure Once the placement is completed, and with the patient in the supine position (prone for anorectal implants), orthogonal films with dummy sources are taken in the
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operating room for verification of the treatment. Loading of the needles with 19*Ir ribbons (the tandem is seldom utilized with 13’Cs)is done in the patient’s room. An 8 mg dose of morphine is given intravenously every 3-5 hr to control the pain associated with the cervical, vaginal, rectal, or prostate implants. The urethral implants require fewer needles of shorter length, so the amount of discomfort is less than that of other perineal plants. Wide-spectrum antibiotic coverage is recommended. Diphenoxylate, 3-4 times a day, is given and the patient receives only intravenous replacement during the implantation period. Patients must remain on their backs (with the exception of anorectal implants, usually they lie on their abdomens); however, the head of the bed can be elevated to 20”. Since these patients generally have about 100 mg Ra eq of iridium, the nursing personnel should be carefully instructed on patient care so as to minimize their exposure. Large bed shields are very useful for decreasing the exposure and allowing more time for nursing care. Once the urine output has stabilized, the Foley catheter is clamped for 4 hr, 200 ml are drained, and the catheter is clamped again. This maneuver maintains bladder distention, decreasing the radiation to both bladder and small intestine. The implant is removed at the patient’s bedside. Premeditation with diazepam, 10 mg orally 0.5 hr before removal, and morphine, up to 10 mg intravenously, given in increments of 2-3 mg, is usually required. The patient is hospitalized for 24 hr after the implant has been removed and is observed for bleeding, fever, or local infection. Perineal sitz baths and vaginal douches are given every 3 hr during this period, and the patient is dismissed with pain medication and indications for perineal hygiene.
DOSIMETRY
February 1984, Volume 10. Number 2
0 Straight
needles
* Angled needles %
@I
0.6 mg Ra EQ
0
@
0.3
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Z 0
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Anterior p--7 \
,p-;
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i
_
.
.
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.
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: ’ 1
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Base of template
Fig. 7. Illustration of the layout for symmetric loading in the treatment of a central bulky tumor. Only straight needles with differential loading (two different activities) are used. No central tandem is utilized.
---
Needle
with lr-192
rtbbon
Cephelad
OF THE MUPIT
Two typical loadings and the corresponding dose rate distributions for the treatment of cancer of the vagina and cervix are shown in Figs. 7-16. In Fig. 7, a symmetric loading for treating large centerline tumors is presented. The 19*Irribbons contain eight seeds each and extend from a depth of 65-135 mm into the tissues (Fig. 8). A total activity of 96mg Ra eq is divided among 14 full-strength ribbons (0.6mg Ra eq/seed) and 12 halfstrength ribbons (0.3 mg Ra eq/seed) (Fig. 7). The resulting dose-rate distributions for transverse planes at depths of 100 (middle of implant), 120, and 140 mm (5 mm beyond end of implant) may be seen in Figs. 9, 10, and Il. The tumor volume, which extends 8 cm laterally, 7 cm caudocephalad, and 4 cm anteroposterior, is best covered by the 75 rad/hr line. Note that the dose-rate decreases to 40 rad/hr 5 to 10 mm outside of these lines and beyond the ends of the implant (Figs. 9-11). This rapid falloff allows sparing of normal tissues and critical structures (bladder and rectum) to a degree not possible with external-beam X-ray treatment. And
III1
I [
Base Of
14 I [r 1
I I
[
I
I--
Y : 120
I,“,1 1 I
I I--
y:‘oo
I
t*mpfat* _____._.
~. .~__._~
65.3210123.55
Fig. 8. Illustration of the geogtric arrangement of the MUPIT, needles, and 19*Irribbons corresponding to layout in Fig. 7. The needles are closed in the distal end (nail configuration) and opened (funnel-shape) in the proximal calculation planes in the y-axis are shown.
end. Dosimetric
Multiple site perineal applicator ??A. MARTINEZ et al.
the maximal dose-rate within the treatment volume is just over 100 rad/hr, occurring in small, isolated volumes at the midplane and around individual seeds. This degree of uniformity cannot be achieved with any standard intracavitary applicator. It is due in part to the judicious choice of full- and half-strength ribbons. When treating patients with tumors that extend laterally on one side of the midplane only, an asymmetric loading is used (Fig. 12). The treatment volume extends 25 mm laterally on one side and from 50 to 65 mm on the other (Fig. 13). In this situation, angled trocars are used in order to cover tissues at distances this far from midline. A total activity of 102.6 mg Ra eq is divided among 18 full- and 10 half-strength ribbons, 15 of which contain eight seeds each (Fig. 12). To avoid hot spots where the application of the three inner angled trocars cross that of the straight trocars, three short ribbons (two with three seeds and one with two seeds) are used (Fig. 13). The corresponding dose-rate distributions are presented in Figs. 14-16. The 75 rad/h line covers the treatment volume in all three transverse views, for depths of 70, 100, and 130 mm. The dose-rate again decreases to 40 rad/h within 10 mm of the 75 rad/h line (Figs. 14-16). Also, small isolated regions occur near midplane and around individual seeds, where the doserate exceeds 100 rad/h. Note that for either symmetric or asymmetric tumors, the dose-rate distribution has been shaped. Near the longitudinal midplane of the patient, the treatment volume is narrowed so as to avoid overdosing the rectum and bladder. For asymmetric tumors, the distribution is again narrowed in the extreme lateral region. This is achieved by the choice of locations in which trocars are inserted. The same shaping can be done in the inferosuperior planes by varying the depth of insertion and the number of seeds per ribbon. This degree of control over the shape of the volume treated cannot be obtained with either external-beam or conventional intracavitary applicators.
303
MUPIT/
20 r/h
I
cm,
6
5
3
4
10
2
1
*
3
4
5
6
1
Fig. 9. Isodose distribution
for symmetric loading in layout of Fig. 7. calculation plane y = 100 mm, or 2cm above the cylinder tip. The 75 rad/hr isodose line covers from the center 4.5 cm laterally on each side. Within 1 cm, the dose rate decreases to 40 radlhr. Calculation
MUPIT
y:
Plane.
120mm
20 r/h
Fig. 10. Isodose distribution for symmetric loading in layout of Fig. 7. Calculation plane y = 120 mm, or 4 cm above the cylinder. Rectum and bladder covered by 40 rad/hr isodose line, while the tumor is covered by 75 rad/hr isodose line.
Calculation
PERITONEAL
Plane.
OUR SERIES
Between June 1976 and December 1982, 78 patients with cervical, vaginal, female urethral, anorectal, and prostatic carcinomas were seen and treated with the MUPIT and its prototypes at the Divisions of Radiation Therapy, Stanford University Medical Center and Mayo Clinic. These patients were referred to us by members of the Divisions of Gynecologic Oncology, General Surgery, and Urology. Most of these patients presented with locally advanced tumors and were treated with a combination of external-beam and implant irradiation. Two patients with early disease who were considered poor surgical risks were treated with the perineal applicator alone. The follow-up for all patients ranged from 3 months to 6.7 years; to date, eight patients have local recurrences. Three patients have major complications. In
20 r/h
L
cm,
11
e
11
5
4
3
2
10 10
’ 12
8
1 3
’ 4
1 5
1 8
7
Fig. 11. Isodose distribution for symmetric loading in layout of Fig. 7. Calculation plane y = 140 mm, or 0.5 cm above the tip of the needles. This represents the dose delivered to the peritoneal cavity.
Radiation Oncology ??Biology ??Physics
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February 1984, Volume IO. Number 2
Straight needles
Calculatton Plane
MUPIT
y=70mm
* Angled needles
4
mg Ra Eq
m
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1
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.
.
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.--’
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. 2
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.
.
.
.
Fig. 14. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane J = 70mm above the first 19*Ir seed at the intersection of the straight and angled needles (see Fig. 13). The 75 rad/hr isodose line covers laterally 2.8 cm on the patient’s left and almost 6 cm on the patient’s right. There is a very small spot of 100 rad/hr.
D
Base of template
/
Fig. 12. Illustration of the layout for asymmetric loading when treating a tumor that extends laterally on one side of the midplane only. Both straight and angled needles are utilized on one side (right). Differential loading (two different activities). No central tandem is utilized.
---
Needle
~4th
lr-
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Cephalad OV 11.5 1
\
\
\ \
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\ I
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Fig. 15. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane y = 100 mm, or 2 cm above the cylinder. The 75 rad/hr isodose line covers laterally 3 cm on the patient’s left and 6.3 cm on the patient’s right. There is a larger area of 100 rad/hr.
Y:‘OO
template i cm7
Fig. 13. Illustration of the geometric arrangement of the MUPIT, needles, and 19’Ir ribbon corresponding to layout of Fig. 12. The needles are closed in the distal end (nail configuration) and opened (funnel-shaped) in the proximal end. Dosimetric calculation planes in the y-axis are shown.
_I - ._,_ -.-^
,_
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1
6
5
4
3
,
1
2
10
/
1
12
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,
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Fig. 16. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane y = 130 mm, or 5 cm above the cylinder. The 75 rad/hr isodose line covers laterally 2.8 cm on the patient’s left and 6.6 cm on the patient’s right. There is a very small area of lOOrad/hr.
Multiple site perineal applicator 0 A. Mmnmz one patient with a large Stage IIB cancer of the cervical
stump, a contracted painful bladder developed 18 months after treatment, necessitating urinary diversion. The second patient had a massive cloacogenic carcinoma involving the rectum, the ischiorectal fossa, and the vagina. This patient developed a necrotic rectal ulcer that failed to heal and required a diverting colostomy 15 months after implantation. The third patient, with Stage IIIB cancer of the cervix and massive involvement of the posterior vaginal wall, developed an ulcer of the anterior rectal mucosa; the ulcer healed with conservative treatment. These three patients are presently free of disease. Minor complications included diarrhea with rectal tenesmus in most patients treated for rectal lesions and temporary dysuria with increase in urinary frequency in patients treated for urethral and prostatic malignancies. Vaginal and rectal mucositis occurred in almost all patients, and in several, perineal wet reactions also developed. Two patients had local infections, and both were treated with antibiotics. For this group of 78 patients, most of whom had locally advanced perineal gynecologic malignancies, our
et al.
305
preliminary results demonstrate a high local control rate (70/78 or 90%) and a low incidence of major complications (3/78 or 3.8%). A complete analysis of the clinical results is the subject of a later paper.” The MUPIT allows wide lateral coverage of the parametrial and pararectal tissues, particularly when the angled holes are utilized, and thus is able to reach tissues that are normally underdosed by other applicators. Moreover, the multiple site capability and large number of trocar guide holes, which permit symmetric and asymmetric placements, provide a flexibility in matching the dose distribution to the tumor volume which had not been attainable before. The fixed and stable geometry of the template and cylinders, maintaining a constant relationship among the sources, tumor, and normal tissues, enable the therapist to more surely maximize tumor dose and minimize normal tissue reactions. For these reasons, we believe that the MUPIT represents an improvement over other single-site intracavitary or interstitial applicators for the treatment of patients with locally advanced perineal and gynecologic malignancies.
REFERENCES 1. Chassagne, D., Attaia, A.B., Pierquin, B.: Rtsultats de
l’endocuriethkrapie par fiis d’iridium 192en gynkologie. J. Radiol. Electr. 51: 223-228,
1970.
2. Chassagne, D., Pierquin, B.: La pl&iocuriethCrapie
des cancers du vagin par moulage plastique avec iridium 192 (prtparation non radio-active): (Note prkliminaire). J. Radiol. Electr. 47: 89-93, 1965.
3. Chau, P.M.: Radiotherapeutic
management of malignant tumors of the vagina. Am. J. Roentgenol. 89: 502-523, 1963.
4. Delclos, L., Fletcher, Moore, B.: Afterloading 666-667,
G.H., Suit, H.D., Sampiere, V., vaginal irradiators. Radiology 96:
1970.
5. Feder, B.H., Syed, A.M.N., Neblett, D.: Treatment
of extensive carcinoma of the cervix with the “transperineal parametrial butterfly”: A preliminary report on the revival of Waterman’s approach. ht. J. Radiat. Oncol. Biol. Phys.
4: 735-742,
6. Fletcher,
1978.
G.H.:
72CL732; 812-828.
Textbook
of Radiotherapy,
3rd edition. Philadelphia,
1980, pp.
Lea & Fe-
biger. Hamberger, A.D., Fletcher, G.H., Wharton, J.T.: Results of treatment of early Stage I carcinoma of the uterine cervix with intracavitary radium alone. Cancer 41: 980-985, 1978. Henschke, U.K.: “Afterloading” applicator for radiation
therapy of carcinoma of the uterus. Radiology 74: 834, 1960. 9. Henschke, U.K., Hilaris, B.S., Mahan, G.D.: Afterloading in interstitial and intracavitary radiation therapy. Am. J. Roentgenol. 90: 386395,
1963.
10. Martinez, A., Herstein, P., Portnuff, J.: Interstitial therapy of perineal and gynecological malignancies. Int. J. Radiat. Oncol. Biol. Phys. 9: 409-416, 1983. 11. Martinez, A., Howes, A., Edmundson, G.K., Cox, R.S.: Combination of external beam irradiation and the multiple-site perineal applicator (MUPIT) for the treatment of locally advanced or recurrent anorectal, prostatic and gynecologic malignancies. Submitted for publication to Int. J. Radiat. Oncoi. Biol. Phys. 12. Perez, C.A., Korba, A., Sharma, S.: Dosimetric considerations in irradiation of carcinoma of the vagina. Int. J. Radiat. Oncol. Biol. Phys. 2: 639-649,
1977.
13. Suit, H.D., Moore, E.B., Fletcher, G.H., Worsnop, R.: Modification of Fletcher ovoid system for afterloading, using standard-sized radium tubes (milligram and microgram). Radiology 81: 126-131, 1963. 14. Syed, A.M.N., Puthawala, A., Neblett, D., George, F.W., III, Myint, U.S., Lipsett, J.A., Jackson, B.R., Flemming, P.A.: Primary treatment of carcinoma of the lower rectum and anal canal by a combination of external irradiation and interstitial implant. Radiology 128: 199-203, 1978.
10,
pp.
297-305 Copyright
C
0360s3016/84 1984 Pergamoo
53.00 + .M) Press Ltd.
??Technical Innovations and Notes A MULTIPLESITE PERINEAL APPLICATOR (MUPIT) FOR TREATMENT OF PROSTATIC, ANORECTAL, AND GYNECOLOGIC MALIGNANCIES ALVARO MARTINEZ, M.D.,‘T~ RICHARD S. Cox, PH.D.2 AND GREGORY K. EDMUNDSON’ ‘Presently from the Department of Oncology, Division of Therapeutic Radiology, Mayo Clinic, Rochester, MN 55905; 2 Department of Radiology, Division of Therapeutic Radiology, Stanford University School of Medicine, Stanford, CA 94305 Recently, transperiwal interstiti&intracevitary applicators have been used to treat IoeaIly limited and advanced perineal and gyneeologic malignancies. We have developed a single afterloading applicator, referred to as the “MUPIT” (Martinez Universal Perineal Interstitial Template), whlcb with its prototypes has been utilized to treat 78 patients with malignancies of the cervix, vagina, female uretbra, perineum, prostate, and anorectal region. The device baslcally consists of two acrylic cylinders, an acrylic template with a predrilled array of holes that serve as guides for trocars, and a cover plate. Some of the guide holes on the template are angled outward to permit a wide lateral coverage without danger of striking the ischlmn. The cylinders have an axial hole large enough to pass a central tandem or a suction tube for the drainage of secretions. Thus, the device allows for the interstitial placement of ‘uIr ribbolrs as well as the intracavitary placement of either ‘uCs tubes or % ribbons. In use, the cylinders are placed in the vagina and rectum and then fastened to the template, so that a fixed geometric relationship among the tumor volume, normal structures, and source placement ls preserved throughout the course of the implantation. Hollow, closed+uul, stainless steel trocars are then inserted through the guide holes that produce optimal coverage of the treatment volume. Appropriate computer programs also have heen developed on a minicomputert for the corresponding dose-rate computations. These programs run with suillcient speed that they may be used for both the planning of the source placement beforehand and the computation of the actual dose-rate distribution obtained. The advantages of tbe system are (1) greater control of the placement of sources relative to the tumor volume and critical structures owing to the fixed geometry provided by the template and cylinders, and (2) improved dose-rate distributions obtained by means of computer-assisted optimization of the source placement and strength during the planning phase. Perineal interstitial applicator, Prostate, Anorectal, Gynecologic tumors.
INTRODUCTION
produce a more homogeneous distribution of radiation dose. The Syed-Neblett parametrial butterAyS and the Syed-Neblett rectal templateI were developed to treat single-site tumors. At the same time, but independently, we were working with a multiple-site single-template interstitial-intracavitary applicator, the MUPIT (Martinez Universal Perineal Interstitial Template), which provides for the use of both 13’Cs tubes and i9*Ir ribbons. In conjunction with external-beam irradiation, the MUPIT (and its prototypes) has been employed in the treatment of 78 patients with primary or recurrent cervical, vaginal, female urethral, perineal, prostatic, and anorectal carcinomas. This report focuses on the description and use of the MUPIT, which provides
Locally advanced perineal and gynecologic malignancies are often difficult to manage by either radical surgery or conventional radiotherapy and present a therapeutic challenge. Presently available intracavitary applicators, such as the Fletcher-Suit,13 the Henschke,’ the Bleodorm3 the Delclos,4 the Chassagne,’ and others, have been effective in controlling early gynecologic cancers, but the local control rates for advanced disease remain ~ow.‘*~~‘~~-~* The most likely explanations are inadequate tumor coverage and tumor-dose inhomogeneity within the implanted volume. The transperineal interstitial-intracavitary applicators are intended to improve target-volume coverage and to
Clinic, for their contributions to the construction of this applicator. Our gratitude to Ms. June M. Henn for her secretarial assistance in the preparation of this manuscript. tPDP 11/SO. Accepted for publication 23 September 1983.
Reprint requests to: Alvaro Martinez, M.D., Division of Therapeutic Radiology, Mayo Clinic, Rochester, MN 55905. Acknowledgements-We thank Mr. Peter Hausman, machine shop of the Stanford Radiotherapy Division, and Mr. Warren N. Lenz, Section of Engineering, from the Mayo 297
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February 1984. Volume IO. Number 2
(1) greater control over the placement of sources relative to the tumor volume and critical anatomic structures than is possible with other applicators and (2) improved dose-rate distributions by utilizing computerized optimization of source placement and source strength during both the planning and the loading phase.
DESCRIPTION OF THE APPLICATOR The MUPIT consists of a flat acrylic template and a flat acrylic cover plate, two sets of acrylic cylinders, obturators, screws, and stainless-steel needles of different lengths (Fig. 1). The template and the cover plate each measure 11 cm vertically, 8 cm horizontally, and 1 cm in thickness. In use, the vertical axis of the template lies roughly along the anteroposterior direction in the patient and the horizontal axis along the lateral direction. To avoid confusion, the terms “inferior” and “superior” will be used, with their customary meanings, when referring to the patient, and the terms “upper” and “lower” will be used when referring to the vertical directions of the template. The template has an array of holes that, for the most part, determine the geometry of source placement with respect to anatomic structures (see Figs. 7 and 12). Three large holes are located along the vertical centerline: the top slotted hole allows the passage of a Foley catheter from the urethra and the center and bottom holes accommodate the vaginal and rectal cylinders, respectively (Fig. 1). To allow for differences in anatomy, the cylinders of each set have two diameters; however, they all have flanges that are well matched to their corresponding holes in the template. Once the appropriate-sized cylinders have been inserted into the patient, the template can be bolted firmly to the cylinders (Fig. 2), thereby fixing the geometric relationship of the template and the anatomic structures. To further fix the geometry, two small holes (located in each corner of the template) are used to suture the assembly to the patient’s perineum. Around the three large holes in the template is a bilaterally symmetric array of small holes that serve as guides for trocars (Fig. 1). The interstitial capability of the MUPIT is utilized by transperineally inserting the trocars through the guide holes and afterloading them with ‘921rseeds. The layout of the guide holes is such that the inserted trocars lie in parallel horizontal planes, perpendicular to the plane of the template (Fig. 3). These planes are spaced vertically at about 1 cm intervals; the actual spacings were determined so as to provide a regular distribution about the large holes. To achieve this geometry, the array is made up of horizontal rows of holes that are of two types: type I rows, wherein the holes are perpendicular to the template (Figs. 3 and 8) interspersed with type II rows, wherein the holes are oblique to the template, angled approximately 13” lat-
Fig. 1. MUPIT contains acrylic predrilled template and cover plate, acrylic cylinders, obturators, screws, and stainless steel needles.
Fig. 2. Acrylic predrilled template attached to both the rectal and vaginal cylinders. Obturator of one of the two cylinders is not used.
erally outward (Figs. 3 and 13). The use of the type II rows allows a wider volume of parametrial or pararectal tissues to be covered at depth without danger of striking the ischium. The holes in each row are spaced 12.5 mm apart. Thus, a volume extending 4cm to either side of midplane can be covered by the use of only type I rows. When type II rows are added, volumes extending laterally outward to 7 cm can be covered at a depth of 14cm. The vaginal and rectal cylinders provide the intracavitary capability of the MUPIT (Fig. 2). A center tube runs the length of each cylinder and is designed to accept either the tandem for 13’Cstubes or a drainage tube. In addition to having a center tube, each cylinder has a flange that carries an array of eight guide holes for the placement of trocars. The guide holes are located on a circle that is slightly smaller than the diameter of the cylinder. and they continue as grooves along the length of the cylinder. This design facilitates the placement of trocars near the vaginal or rectal wall.
Multiple site perineal applicator ??A. MARTINEZ et d.
299
cylinders of the appropriate diameter and length are chosen. The lateral, anterior, and posterior extents of the treatment volume are determined, and the corresponding lateral, upper, and lower guide holes in the template are selected. The superior extension of the tumor determines the depth to which the trocars must be placed, and the inferior extent determines the number of sources per ribbon required for adequate coverage of the treatment volume. These data (the identification of cylinders and guide holes utilized, the depth of insertion of the trocars and tandem, and the number of sources per ribbon) serve as input for the treatment-planning computer program. Since the geometric relationship of the cylinders and trocars is fixed, the three-dimensional positions of all the individual seeds and tubes can be calculated. Dose rates at any point can then be determined by furnishing the activity of the sources chosen from the current inventory. Distributions of dose rate are computed in crosssectional planes (parallel to the template) at depths specified by the user, usually every few centimeters throughout the treatment volume. If the dose-rate distribution is judged to be inadequate, modifications are made in the plan and the distribution is recalculated. Once a plan is accepted, the physician knows exactly what protocol to follow in the operating room and what the resulting dose-rate distribution will be, since the geometry is completely fixed by the applicator. If the chosen plan cannot be executed in the operating room, further planning is required between the time of placement and that of afterloading. with two rows of straight needles on the right and three rows of straight needles and one row of angled needles on the left. Different lengths on each side. Fig. 3. MUPIT
IMPLANTATION
PROCEDURE
Patient preparation
are modified 17-gauge needles that have a bore large enough to accept the ig21rribbons (Fig. 3). The pointed end is sealed with a small fillet of solder and reground to resemble the point of a nail. The opposite end is flared to facilitate loading (Fig. 3). To cover treatment volumes that may vary widely in depth from patient to patient, several sets of trocars of different lengths are available. The trocars
PREIMPLANT
PLANNING
The patient is seen conjointly at the subspecialty clinic corresponding to the site of origin of the tumor. When the patient becomes a candidate for primary radiotherapy, a complete workup is obtained and the need for external-beam therapy, in addition to the implant, is assessed. Most patients are treated with a combination of external-beam megavoltage irradiation and the MUPIT implant. A discussion of the integration of these two modalities is a subject of another publication. The type of anesthesia is selected, and the factors involved in treatment planning are determined. Vaginal and rectal
After the planning session has been completed, the implant procedure is scheduled. For bowel preparation, the patient is advised to take clear liquids the day before admission and is hospitalized 24 hr before the implantation. Preoperative laboratory studies include complete blood count with differential platelet count, coagulation studies, electrolytes, urinalysis, chest roentgenogram, and electrocardiogram. If the patient is well hydrated and in good general condition, one bottle of magnesium citrate is given the morning of admission. One gram of neomycin every 4 hr and 1 g of erythromycin every 6 hr are administered orally. Tap water enemas are given until the return is clear; these are followed by a retention enema consisting of 0.1% neomycin in 500 ml of normal saline, followed again by tap water enemas until the return is clear. The enemas are usually completed by 4: 00 p.m. on the evening before implantation. The perineum is shaved. Female patients also receive two vaginal douches with povidone-iodine. On the morning of implantation, thigh hoses are fitted and fluids are started intravenously. Potassium replacement is added, if indicated. In the operating room, a
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pelvic examination with an anosigmoidoscope or a cystoscope is performed when required with the patient under general anesthesia. The extent of the tumor is carefully reassessed, and radiopaque markers delineating the tumor margins are placed. Cervix and vaginal implantation. The patient is placed in the lithotomy position and several 1-O silk sutures are stitched through the normal tissues (whenever possible) or tumor (or both). By applying gentle traction on these sutures, the tumor can be immobilized during insertion of the trocar. A Foley catheter with diatrizoate in the balloon is left in the bladder. If necessary, the cervix is dilated, the uterine canal is sounded, and a tandem is inserted. The sutures are pulled through the central orifice of the vaginal cylinder, and the cylinder is slipped over the tandem into the vagina and fixed to each other with a set screw. The template is then attached to the cylinder and sutured to the patient’s perineum; special care is taken to avoid tilting the template. The physician, utilizing a double glove, places a finger in the rectum. While the assistant pulls gently on the sutures, he pushes the first needle transperineally through the tissues to the appropriate depth. Next, the needles nearest the rectum are then inserted while gentle tension is maintained on the sutures. Care is taken to avoid either perforating the rectal mucosa or leaving the free-floating needles in the rectal lumen. After the surgeon’s finger is removed from the rectum, the cylinder is placed in the rectum and attached to the template. This assures that a fixed distance between the vaginal and the rectal canal is maintained and that the posterior rectal wall is held away from the radioactive sources. A rectal tube is inserted for removal of flatus and drainage of secretions. The remaining needles are placed around the vaginal cylinder to the preset depth. The sutures are removed. The template is sutured to the perineum with 1-O silk sutures, and the cover plate is placed over the sutured template and screwed to it to prevent displacement of the needles (Fig. 4). Sterile gauze is placed between the skin and the template (Fig. 5). The Foley catheter is attached to the draining bag. Care must be taken to keep the bladder distended so as to decrease the radiation to this organ and to displace the small bowel away from the sources of radiation. The rectal tube is connected to intermittent suction. Rectal implantation In the operating room, the patient is placed in the knee-chest position and a Foley catheter is inserted. The preselected rectal cylinder is inserted and fixed to the template. The template is sutured to the skin with silk sutures. The needles are then inserted transperineally to the preset depth. When the lesion is in the anterior anorectal wall, in males, care must be taken to avoid perforating the prostatic urethra. In females, the vaginal cylinder is utilized to keep a fixed distance between the rectal and vaginal walls. A rectal tube, applied to
February 1984. Volume 10, Number 2
intermittent suction, is inserted through the center hole of the cylinder. Generous gauze padding is utilized to cover the template. Prostate implantation After the staging pelvic lymphadenectomy is completed, the endopelvic fascia is opened and the prostate gland, seminal vesicles, and posterolateral pelvic wall are exposed. Metal markers are placed to delineate the boundary of the tumor. With *the patient in the lithotomy position and the surgeon’s one hand in the peritoneal cavity, the guide needle is positioned transperineally just below the pubic bone and pushed into the peritoneal cavity, until a satisfactory superior margin is obtained. This needle is then removed, and the depth of the insertion is measured so the correct needle length can be determined. The template, “upside down,” is applied against the perineum. Utilizing the previous skin puncture and needle tract, the most superior needle is inserted to the preset depth. The remainder of the needles are -
Fig. 4. MUPIT sutured to patient’s perineum. Foley catheter, cylinders, and needles in place. The funnel-like configuration on the end of each needle facilitates afterloading. The cover plate is screwed to the template to keep the needles and
radioactive material in place.
Multiple site perineal applicator ??A. MARTINEZer al.
301
Complated MUPIT implant in a patient with Stage IIIB cancer of the cervix.
Fig. 5.
then positioned transperineally; however, the spacing of the tips is checked intraperitoneally. Rectal examination is performed to be sure that no needles have penetrated the rectal mucosa. The rectal cylinder is inserted, and a rectal tube is secured to the skin and connected to intermittent suction. The template is sutured to the skin with 1-O silk sutures and the cover plate is screwed to the template. The abdominal skin is closed (Fig. 6). A Foley catheter with bladder distention is maintained until the MUPIT is removed. Female urethral implantation
Although the patient is hospitalized the afternoon before the procedure, a less extensive bowel preparation is ordered. In the operating room, with the patient in the lithotomy position, several silk sutures are stitched through the tumor in order to immobilize the tumor during insertion of the needles. A three-way Foley catheter, 14-F to 16-F, is selected. Methylene blue is injected into the third lumen, and a small hole is made in the catheter. A trocar with a blind end is introduced through this hole into the Foley catheter and is advanced
Fig. 6. MUPIT implant with the template “upside down” in a patient with Stage C cancer of the prostate. Note the funnel-like configuration of needles. Cover plate not yet placed.
to the base of the balloon. This will allow afterloading of “*Ir inside the urethra. The tip of the catheter is passed through the plate hole and inserted into the urethra. The balloon is filled with 5 ml of diatrizoate, and the bladder is drained. The template is sutured to the perineum, and the periurethral needles are inserted to the preset depth. The vaginal cylinder is introduced to increase the stability of the applicator, to allow implantation of the anterior vaginal wall, and to displace the posterior vaginal wall away from the sources. Gauze padding is utilized around the template, and the entire applicator is covered. Postoperative procedure Once the placement is completed, and with the patient in the supine position (prone for anorectal implants), orthogonal films with dummy sources are taken in the
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Radiation Oncology ??Biology ??Physics
operating room for verification of the treatment. Loading of the needles with 19*Ir ribbons (the tandem is seldom utilized with 13’Cs)is done in the patient’s room. An 8 mg dose of morphine is given intravenously every 3-5 hr to control the pain associated with the cervical, vaginal, rectal, or prostate implants. The urethral implants require fewer needles of shorter length, so the amount of discomfort is less than that of other perineal plants. Wide-spectrum antibiotic coverage is recommended. Diphenoxylate, 3-4 times a day, is given and the patient receives only intravenous replacement during the implantation period. Patients must remain on their backs (with the exception of anorectal implants, usually they lie on their abdomens); however, the head of the bed can be elevated to 20”. Since these patients generally have about 100 mg Ra eq of iridium, the nursing personnel should be carefully instructed on patient care so as to minimize their exposure. Large bed shields are very useful for decreasing the exposure and allowing more time for nursing care. Once the urine output has stabilized, the Foley catheter is clamped for 4 hr, 200 ml are drained, and the catheter is clamped again. This maneuver maintains bladder distention, decreasing the radiation to both bladder and small intestine. The implant is removed at the patient’s bedside. Premeditation with diazepam, 10 mg orally 0.5 hr before removal, and morphine, up to 10 mg intravenously, given in increments of 2-3 mg, is usually required. The patient is hospitalized for 24 hr after the implant has been removed and is observed for bleeding, fever, or local infection. Perineal sitz baths and vaginal douches are given every 3 hr during this period, and the patient is dismissed with pain medication and indications for perineal hygiene.
DOSIMETRY
February 1984, Volume 10. Number 2
0 Straight
needles
* Angled needles %
@I
0.6 mg Ra EQ
0
@
0.3
mg Ra Eq
Z 0
Opening for
Anterior p--7 \
,p-;
Holes for suture
E&c;
i
_
.
.
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.
*
Rectal
: ’ 1
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Base of template
Fig. 7. Illustration of the layout for symmetric loading in the treatment of a central bulky tumor. Only straight needles with differential loading (two different activities) are used. No central tandem is utilized.
---
Needle
with lr-192
rtbbon
Cephelad
OF THE MUPIT
Two typical loadings and the corresponding dose rate distributions for the treatment of cancer of the vagina and cervix are shown in Figs. 7-16. In Fig. 7, a symmetric loading for treating large centerline tumors is presented. The 19*Irribbons contain eight seeds each and extend from a depth of 65-135 mm into the tissues (Fig. 8). A total activity of 96mg Ra eq is divided among 14 full-strength ribbons (0.6mg Ra eq/seed) and 12 halfstrength ribbons (0.3 mg Ra eq/seed) (Fig. 7). The resulting dose-rate distributions for transverse planes at depths of 100 (middle of implant), 120, and 140 mm (5 mm beyond end of implant) may be seen in Figs. 9, 10, and Il. The tumor volume, which extends 8 cm laterally, 7 cm caudocephalad, and 4 cm anteroposterior, is best covered by the 75 rad/hr line. Note that the dose-rate decreases to 40 rad/hr 5 to 10 mm outside of these lines and beyond the ends of the implant (Figs. 9-11). This rapid falloff allows sparing of normal tissues and critical structures (bladder and rectum) to a degree not possible with external-beam X-ray treatment. And
III1
I [
Base Of
14 I [r 1
I I
[
I
I--
Y : 120
I,“,1 1 I
I I--
y:‘oo
I
t*mpfat* _____._.
~. .~__._~
65.3210123.55
Fig. 8. Illustration of the geogtric arrangement of the MUPIT, needles, and 19*Irribbons corresponding to layout in Fig. 7. The needles are closed in the distal end (nail configuration) and opened (funnel-shape) in the proximal calculation planes in the y-axis are shown.
end. Dosimetric
Multiple site perineal applicator ??A. MARTINEZ et al.
the maximal dose-rate within the treatment volume is just over 100 rad/hr, occurring in small, isolated volumes at the midplane and around individual seeds. This degree of uniformity cannot be achieved with any standard intracavitary applicator. It is due in part to the judicious choice of full- and half-strength ribbons. When treating patients with tumors that extend laterally on one side of the midplane only, an asymmetric loading is used (Fig. 12). The treatment volume extends 25 mm laterally on one side and from 50 to 65 mm on the other (Fig. 13). In this situation, angled trocars are used in order to cover tissues at distances this far from midline. A total activity of 102.6 mg Ra eq is divided among 18 full- and 10 half-strength ribbons, 15 of which contain eight seeds each (Fig. 12). To avoid hot spots where the application of the three inner angled trocars cross that of the straight trocars, three short ribbons (two with three seeds and one with two seeds) are used (Fig. 13). The corresponding dose-rate distributions are presented in Figs. 14-16. The 75 rad/h line covers the treatment volume in all three transverse views, for depths of 70, 100, and 130 mm. The dose-rate again decreases to 40 rad/h within 10 mm of the 75 rad/h line (Figs. 14-16). Also, small isolated regions occur near midplane and around individual seeds, where the doserate exceeds 100 rad/h. Note that for either symmetric or asymmetric tumors, the dose-rate distribution has been shaped. Near the longitudinal midplane of the patient, the treatment volume is narrowed so as to avoid overdosing the rectum and bladder. For asymmetric tumors, the distribution is again narrowed in the extreme lateral region. This is achieved by the choice of locations in which trocars are inserted. The same shaping can be done in the inferosuperior planes by varying the depth of insertion and the number of seeds per ribbon. This degree of control over the shape of the volume treated cannot be obtained with either external-beam or conventional intracavitary applicators.
303
MUPIT/
20 r/h
I
cm,
6
5
3
4
10
2
1
*
3
4
5
6
1
Fig. 9. Isodose distribution
for symmetric loading in layout of Fig. 7. calculation plane y = 100 mm, or 2cm above the cylinder tip. The 75 rad/hr isodose line covers from the center 4.5 cm laterally on each side. Within 1 cm, the dose rate decreases to 40 radlhr. Calculation
MUPIT
y:
Plane.
120mm
20 r/h
Fig. 10. Isodose distribution for symmetric loading in layout of Fig. 7. Calculation plane y = 120 mm, or 4 cm above the cylinder. Rectum and bladder covered by 40 rad/hr isodose line, while the tumor is covered by 75 rad/hr isodose line.
Calculation
PERITONEAL
Plane.
OUR SERIES
Between June 1976 and December 1982, 78 patients with cervical, vaginal, female urethral, anorectal, and prostatic carcinomas were seen and treated with the MUPIT and its prototypes at the Divisions of Radiation Therapy, Stanford University Medical Center and Mayo Clinic. These patients were referred to us by members of the Divisions of Gynecologic Oncology, General Surgery, and Urology. Most of these patients presented with locally advanced tumors and were treated with a combination of external-beam and implant irradiation. Two patients with early disease who were considered poor surgical risks were treated with the perineal applicator alone. The follow-up for all patients ranged from 3 months to 6.7 years; to date, eight patients have local recurrences. Three patients have major complications. In
20 r/h
L
cm,
11
e
11
5
4
3
2
10 10
’ 12
8
1 3
’ 4
1 5
1 8
7
Fig. 11. Isodose distribution for symmetric loading in layout of Fig. 7. Calculation plane y = 140 mm, or 0.5 cm above the tip of the needles. This represents the dose delivered to the peritoneal cavity.
Radiation Oncology ??Biology ??Physics
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February 1984, Volume IO. Number 2
Straight needles
Calculatton Plane
MUPIT
y=70mm
* Angled needles
4
mg Ra Eq
m
0.6
$z
0.3 mg Ra Eq
Z 0
Anterior
/-,
Holes for suture
Opening for Foley cathet er
1
Vaginal cylinder
Rectal cylinder
.
.
.
.\
.--’
j
. 2
_
”
”
.
.
.
.
Fig. 14. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane J = 70mm above the first 19*Ir seed at the intersection of the straight and angled needles (see Fig. 13). The 75 rad/hr isodose line covers laterally 2.8 cm on the patient’s left and almost 6 cm on the patient’s right. There is a very small spot of 100 rad/hr.
D
Base of template
/
Fig. 12. Illustration of the layout for asymmetric loading when treating a tumor that extends laterally on one side of the midplane only. Both straight and angled needles are utilized on one side (right). Differential loading (two different activities). No central tandem is utilized.
---
Needle
~4th
lr-
192 rbbon
Cephalad OV 11.5 1
\
\
\ \
\I
\ I
Base
of
’ I
\
nml
c
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I
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131
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I
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( Top of needle -
)
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Fig. 15. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane y = 100 mm, or 2 cm above the cylinder. The 75 rad/hr isodose line covers laterally 3 cm on the patient’s left and 6.3 cm on the patient’s right. There is a larger area of 100 rad/hr.
Y:‘OO
template i cm7
Fig. 13. Illustration of the geometric arrangement of the MUPIT, needles, and 19’Ir ribbon corresponding to layout of Fig. 12. The needles are closed in the distal end (nail configuration) and opened (funnel-shaped) in the proximal end. Dosimetric calculation planes in the y-axis are shown.
_I - ._,_ -.-^
,_
I
1
6
5
4
3
,
1
2
10
/
1
12
3
,
4
Fig. 16. Isodose distribution for asymmetric loading in layout of Fig. 12. Calculation plane y = 130 mm, or 5 cm above the cylinder. The 75 rad/hr isodose line covers laterally 2.8 cm on the patient’s left and 6.6 cm on the patient’s right. There is a very small area of lOOrad/hr.
Multiple site perineal applicator 0 A. Mmnmz one patient with a large Stage IIB cancer of the cervical
stump, a contracted painful bladder developed 18 months after treatment, necessitating urinary diversion. The second patient had a massive cloacogenic carcinoma involving the rectum, the ischiorectal fossa, and the vagina. This patient developed a necrotic rectal ulcer that failed to heal and required a diverting colostomy 15 months after implantation. The third patient, with Stage IIIB cancer of the cervix and massive involvement of the posterior vaginal wall, developed an ulcer of the anterior rectal mucosa; the ulcer healed with conservative treatment. These three patients are presently free of disease. Minor complications included diarrhea with rectal tenesmus in most patients treated for rectal lesions and temporary dysuria with increase in urinary frequency in patients treated for urethral and prostatic malignancies. Vaginal and rectal mucositis occurred in almost all patients, and in several, perineal wet reactions also developed. Two patients had local infections, and both were treated with antibiotics. For this group of 78 patients, most of whom had locally advanced perineal gynecologic malignancies, our
et al.
305
preliminary results demonstrate a high local control rate (70/78 or 90%) and a low incidence of major complications (3/78 or 3.8%). A complete analysis of the clinical results is the subject of a later paper.” The MUPIT allows wide lateral coverage of the parametrial and pararectal tissues, particularly when the angled holes are utilized, and thus is able to reach tissues that are normally underdosed by other applicators. Moreover, the multiple site capability and large number of trocar guide holes, which permit symmetric and asymmetric placements, provide a flexibility in matching the dose distribution to the tumor volume which had not been attainable before. The fixed and stable geometry of the template and cylinders, maintaining a constant relationship among the sources, tumor, and normal tissues, enable the therapist to more surely maximize tumor dose and minimize normal tissue reactions. For these reasons, we believe that the MUPIT represents an improvement over other single-site intracavitary or interstitial applicators for the treatment of patients with locally advanced perineal and gynecologic malignancies.
REFERENCES 1. Chassagne, D., Attaia, A.B., Pierquin, B.: Rtsultats de
l’endocuriethkrapie par fiis d’iridium 192en gynkologie. J. Radiol. Electr. 51: 223-228,
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2. Chassagne, D., Pierquin, B.: La pl&iocuriethCrapie
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