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External beam radiation therapy and retinodlastoma: Long term results in the comparison of two techniques
Copyright
Medical Dosimetry, 0 1997 American
Vol. 22. No. 2. pp. 16% 165. 1997 Association of Medical Dosimetrists Printed in the USA. All rights reserved 095%3947/96 $17.00 + .OO
PI1 SO958-3947(97)00060-S
ELSEVIER
0 Literature Review KEVIN
R. JONES
THE EFFECTIVENESS OF IMMOBILIZATION PROSTATE IRRADIATION
course of radiotherapy for prostate cancer when compared to treatments set up without an immobilization device.
DURING
Gunilla C. Bentel, R.N.. R.T.T., Lawrence B. Marks, M.D., George W. Sherouse, Ph.D., David P. Spencer, Ph.D., and Mitchell S. Anscher M.D. Department
of Radiation Oncology, Durham NC
EXTERNAL BEAM RADIATION THERAPY RETINOBLASTOMA: LONG TERM RESULTS COMPARISON OF Two TECHNIQUES
Duke University,
International Journal of Radiation Oncology. Biology, Physics. Volume 31, Number 1, 1995, pp. 141-148
Laurie E. Blach, M.D., Beryl MC Cormick. David H. Abramson, M.D.
AND IN THE
M.D., and
Memorial Sloan Kettering Cancer Center and New York Hospital-Cornell Medical Center, New York, NY
During the past few years many Radiation Oncology Departments were in the process of analyzing and selecting immobilization devices. The purpose of this article is to evaluate the difference of using no immobilization and using hemibody foam cast to immobilize patients being treated for prostate cancer. In this study 74 patients were treated with pelvic irradiation, 44 of those patients were immobilized in a custom made hemibody foam cast. Thirty patients were treated without an immobilization device. The immobilization device was constructed on the CT scan table prior to performing the pelvic CT scan. The device extended from the mid chest to below the bottom of the feet. The article then goes on to discuss the exact dimensions of the immobilization device. The patients in both groups were simulated during which the central axes and field perimeters were marked. The article then goes on to discuss the importance of excessive markings on the foam device. The markings on the device were considered to be more reliable for setting the patient up. The article then gives a detailed description as to where on the foam cast the marks should be made. All patients except three were treated with a four field box, isocentric technique. The article then goes on to discuss how the port film review was conducted. The purpose of the port film review was to determine the reproducibility of patient setup throughout the 6-7 week course of treatment under routine clinical conditions. All port films were reviewed by someone other than the monitoring physician. This review was not to determine whether the initial judgment in accuracy of the isocenter placement was proper, but to record the observations made by the monitoring physician. The author then shows in table form, a comparison of alignment errors comparing with and without immobilizing patients. In conclusion, the article states that this customized immobilization device has been shown to significantly improve the reproducibility of patient positioning over a 7 week
International Journal of Radiation Oncology, Biology, Physics. Volume 35, Number 1. 1996, pp. 45-51 The purpose of this article is to compare long term control, eye conservation rate, and ocular complications in children with retinoblastoma treated with two different external beam radiation therapy (EBRT) techniques. Before, children with retinoblastoma were treated with enucleation. Since the successful use of radiation therapy in the treatment of this disease was documented, EBRT evolved into a standard eye conserving treatment for children with intraocular bilateral disease. The traditional method of EBRT was a single lateral “D” shaped field with the anterior border placed at the outer canthus. This method left the anterior portion of the retina untreated and resulted in recurrences in this region. The article then goes on and discusses two eye sparing EBRT techniques. From 1979- 1991 395 children with retinoblastoma were evaluated and 123 children were referred for Radiation Therapy. The two EBRT treatment groups were balanced with regard to prognostic variables including Reese, Ellsworth classification group # of unilateral eyes, initial age of diagnosis, administration of chemotherapy, and family history of retinoblastoma. Next. the article discusses and describes in detail the ALS (anterior lens sparing technique) and the MLB (modified lateral technique). Daily doses and isodose levels are also mentioned. For patients with unilateral disease, the single oblique technique field described by Schipper was modified in several ways. This method is described in detail in this article. Results: A detailed comparison between the techniques is presented in table form. The 5-8 year actuarial local control or freedom from relapse was improved using the MLB technique. A comparsion of eye survival (no enucleation) for the two techniques is presented also in table form.
163
164
Medical Dosimetry
The article then lists external beam results done at many centers from 1956- 1991. In conclusion: There is a significant improvement in local control of the irradiated eyes when a modified lateral beam technique is used as compared to an anterior lens sparing technique. Survival endpoints and complications of the two techniques are similar. Since there is an increase in cataract development and other potential complications using an anterior approach without lens blocking, the author recommends the use of a modified lateral beam approach for the treatment of intraocular retinoblastoma with external beam radiation therapy.
JANICE
McKEAGUE
A QUANTITATIVE ASESSMENT OF STANDARD CUSTOMIZED MIDLINE SHIELD CONSTRUCTION INVASIVE CERVICAL CARCINOMA
vs. FOR
Aaron H. Wolfson, M.D., May Abdel-Wahab, M.D., Arnold M. Markoe, M.D., Sc.D., William J. Raub, Jr., Ms.PH., David Diaz, R.T.T., Joseph J. Desmond, R.T.T., and Joseph Y. Ting, Ph.D. Department of Radiation Oncology, University of Miami, Sysvester Comprehensive Cancer Center, Miami, FL International
Journal of Radiation Oncology. Number 1, January 1997
Volume
37,
This article describes the comparison between the use of a standard block vs. a customized fabricated midline shield for delivering homogeneous radiotherapy to patients with invasive cervical carcinoma during the parametrial boost portion of extreme beam irradiation. The patients chosen for evaluation were divided into two groups: patients irradiated with a standard rectangular 5HVL midline block, and those irradiated with a midline shield that was fabricated following the “Point A” isodose distribution of the brachytherapy implant. This distribution was superimposed onto each patient’s pelvis AP simulation films. An evaluation between the placement of the standard block and the location of the “Point A” isodose line was carried out with the following important parameters in mind: a) Did the midline of the tandem deviate to the right or left of the patients midline? b) note the angle of deviation between the patients midline and the axis of the tandem: c) note the distance deviated from the lateral aspect of the standard block to the “Point A” distribution on the side of tandem deviation. The total dose to “Point A” was recalculated and the percent deviation determined if a deviation of the tandem to the right or left of the longitudinal midline was present. Since the original pescription point, which is defined as “Point A” refers to the plane of the tandem, it seems reasonable to include the lateral deviation of the tandem when fabricating the midline shield. It has been reported that the shaped midline shield fabricated to the “Point A” isodose distribution should be employed during parametrial irradiation. It not only reduces the dose to the
Volume 22, Number 2, 1997 bladder and rectum but also helps to prevent vaginal vault necrosis. If further parametrial radiotherapy is indicated after a second implant procedure, a new midline block is cut from the “Point A” isodose distribution of the latter implant. From the survey presented in this article, it seems reasonable to construct the midline shield following these parameters: a) the inferior border of the shield should coincide with that of the whole pelvic external beam field to prevent possible vaginal vault necrosis, b) the cephalad margin of the shield at the most inferior to middle aspect of the sacroiliac joints so not to block the dose to the common iliac nodes, c) depending on the deviation of the “Point A” isodose distribution with respect to the lateral edge of a standard block, possible under dosing of the tumor is possible. The customized shield would be shaped in order to avoid under dosing. One of the objectives of radiotherapy is to achieve dose homogeneity ( 25% ) to tumor without excessively irradiating normal tissues. However, depending on the extent of disease lateral to the midline of the patient’s pelvis, the potential for inadequate dosing exists. Hence, further studies, including three dimensional treatment planning may be indicated concerning the fabrication of the midline shield for patients with invasive cervical carcinoma.
DOSIMETRIC EVALUATION OF LEAD AND TUNGSTEN SHIELDS IN ELECTRON BEAM TREATMENT
EYE
Almon S. Shiu, Ph.D.,* Samuel S. Tung, M.S.,* Robert J. Gastorf, MS.,* Kenneth R. Hogstrom, Ph.D.,* William H. Morrison, M.D.** and Lester J. Peters, M.D.** *Department of Radiation Physicis and **Department Clinical Radiotherapy, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030
of
International Journal of Radiation Oncology, Biology, Physics. Volume 35. Number 3, June 1996 This article describes the inadequate protection provided by commercially available eye shields designed for orthovoltage x-rays and used for treating with electron beam energies equal to or greater than 6 MeV. A similar eye shield constructed of tungsten was designed and fabricated. The advantages of this shield over the lead shield were discussed. An eye phantom was designed and built of nontransparent polystyrene to simulate the shape of an eyeball. Electron transmission measurements of the eye shields were made using x v-2 film. One film each with and without the eye shield was exposed for each electron beam energy. None of the commercially available lead eye shields covered with plastic coating offered sufficient protection for 6 MeV electrons. To adequately block 6 MeV and 9 MeV electrons, the resulting eye shields are too thick to fit under the eyelid. As for the tungsten eye shield, a thickness of approximately 3 mm. of tungsten would adequately block 9 MeV
Medical Dosimetry, 0 1997 American
Vol. 22. No. 2. pp. 16% 165. 1997 Association of Medical Dosimetrists Printed in the USA. All rights reserved 095%3947/96 $17.00 + .OO
PI1 SO958-3947(97)00060-S
ELSEVIER
0 Literature Review KEVIN
R. JONES
THE EFFECTIVENESS OF IMMOBILIZATION PROSTATE IRRADIATION
course of radiotherapy for prostate cancer when compared to treatments set up without an immobilization device.
DURING
Gunilla C. Bentel, R.N.. R.T.T., Lawrence B. Marks, M.D., George W. Sherouse, Ph.D., David P. Spencer, Ph.D., and Mitchell S. Anscher M.D. Department
of Radiation Oncology, Durham NC
EXTERNAL BEAM RADIATION THERAPY RETINOBLASTOMA: LONG TERM RESULTS COMPARISON OF Two TECHNIQUES
Duke University,
International Journal of Radiation Oncology. Biology, Physics. Volume 31, Number 1, 1995, pp. 141-148
Laurie E. Blach, M.D., Beryl MC Cormick. David H. Abramson, M.D.
AND IN THE
M.D., and
Memorial Sloan Kettering Cancer Center and New York Hospital-Cornell Medical Center, New York, NY
During the past few years many Radiation Oncology Departments were in the process of analyzing and selecting immobilization devices. The purpose of this article is to evaluate the difference of using no immobilization and using hemibody foam cast to immobilize patients being treated for prostate cancer. In this study 74 patients were treated with pelvic irradiation, 44 of those patients were immobilized in a custom made hemibody foam cast. Thirty patients were treated without an immobilization device. The immobilization device was constructed on the CT scan table prior to performing the pelvic CT scan. The device extended from the mid chest to below the bottom of the feet. The article then goes on to discuss the exact dimensions of the immobilization device. The patients in both groups were simulated during which the central axes and field perimeters were marked. The article then goes on to discuss the importance of excessive markings on the foam device. The markings on the device were considered to be more reliable for setting the patient up. The article then gives a detailed description as to where on the foam cast the marks should be made. All patients except three were treated with a four field box, isocentric technique. The article then goes on to discuss how the port film review was conducted. The purpose of the port film review was to determine the reproducibility of patient setup throughout the 6-7 week course of treatment under routine clinical conditions. All port films were reviewed by someone other than the monitoring physician. This review was not to determine whether the initial judgment in accuracy of the isocenter placement was proper, but to record the observations made by the monitoring physician. The author then shows in table form, a comparison of alignment errors comparing with and without immobilizing patients. In conclusion, the article states that this customized immobilization device has been shown to significantly improve the reproducibility of patient positioning over a 7 week
International Journal of Radiation Oncology, Biology, Physics. Volume 35, Number 1. 1996, pp. 45-51 The purpose of this article is to compare long term control, eye conservation rate, and ocular complications in children with retinoblastoma treated with two different external beam radiation therapy (EBRT) techniques. Before, children with retinoblastoma were treated with enucleation. Since the successful use of radiation therapy in the treatment of this disease was documented, EBRT evolved into a standard eye conserving treatment for children with intraocular bilateral disease. The traditional method of EBRT was a single lateral “D” shaped field with the anterior border placed at the outer canthus. This method left the anterior portion of the retina untreated and resulted in recurrences in this region. The article then goes on and discusses two eye sparing EBRT techniques. From 1979- 1991 395 children with retinoblastoma were evaluated and 123 children were referred for Radiation Therapy. The two EBRT treatment groups were balanced with regard to prognostic variables including Reese, Ellsworth classification group # of unilateral eyes, initial age of diagnosis, administration of chemotherapy, and family history of retinoblastoma. Next. the article discusses and describes in detail the ALS (anterior lens sparing technique) and the MLB (modified lateral technique). Daily doses and isodose levels are also mentioned. For patients with unilateral disease, the single oblique technique field described by Schipper was modified in several ways. This method is described in detail in this article. Results: A detailed comparison between the techniques is presented in table form. The 5-8 year actuarial local control or freedom from relapse was improved using the MLB technique. A comparsion of eye survival (no enucleation) for the two techniques is presented also in table form.
163
164
Medical Dosimetry
The article then lists external beam results done at many centers from 1956- 1991. In conclusion: There is a significant improvement in local control of the irradiated eyes when a modified lateral beam technique is used as compared to an anterior lens sparing technique. Survival endpoints and complications of the two techniques are similar. Since there is an increase in cataract development and other potential complications using an anterior approach without lens blocking, the author recommends the use of a modified lateral beam approach for the treatment of intraocular retinoblastoma with external beam radiation therapy.
JANICE
McKEAGUE
A QUANTITATIVE ASESSMENT OF STANDARD CUSTOMIZED MIDLINE SHIELD CONSTRUCTION INVASIVE CERVICAL CARCINOMA
vs. FOR
Aaron H. Wolfson, M.D., May Abdel-Wahab, M.D., Arnold M. Markoe, M.D., Sc.D., William J. Raub, Jr., Ms.PH., David Diaz, R.T.T., Joseph J. Desmond, R.T.T., and Joseph Y. Ting, Ph.D. Department of Radiation Oncology, University of Miami, Sysvester Comprehensive Cancer Center, Miami, FL International
Journal of Radiation Oncology. Number 1, January 1997
Volume
37,
This article describes the comparison between the use of a standard block vs. a customized fabricated midline shield for delivering homogeneous radiotherapy to patients with invasive cervical carcinoma during the parametrial boost portion of extreme beam irradiation. The patients chosen for evaluation were divided into two groups: patients irradiated with a standard rectangular 5HVL midline block, and those irradiated with a midline shield that was fabricated following the “Point A” isodose distribution of the brachytherapy implant. This distribution was superimposed onto each patient’s pelvis AP simulation films. An evaluation between the placement of the standard block and the location of the “Point A” isodose line was carried out with the following important parameters in mind: a) Did the midline of the tandem deviate to the right or left of the patients midline? b) note the angle of deviation between the patients midline and the axis of the tandem: c) note the distance deviated from the lateral aspect of the standard block to the “Point A” distribution on the side of tandem deviation. The total dose to “Point A” was recalculated and the percent deviation determined if a deviation of the tandem to the right or left of the longitudinal midline was present. Since the original pescription point, which is defined as “Point A” refers to the plane of the tandem, it seems reasonable to include the lateral deviation of the tandem when fabricating the midline shield. It has been reported that the shaped midline shield fabricated to the “Point A” isodose distribution should be employed during parametrial irradiation. It not only reduces the dose to the
Volume 22, Number 2, 1997 bladder and rectum but also helps to prevent vaginal vault necrosis. If further parametrial radiotherapy is indicated after a second implant procedure, a new midline block is cut from the “Point A” isodose distribution of the latter implant. From the survey presented in this article, it seems reasonable to construct the midline shield following these parameters: a) the inferior border of the shield should coincide with that of the whole pelvic external beam field to prevent possible vaginal vault necrosis, b) the cephalad margin of the shield at the most inferior to middle aspect of the sacroiliac joints so not to block the dose to the common iliac nodes, c) depending on the deviation of the “Point A” isodose distribution with respect to the lateral edge of a standard block, possible under dosing of the tumor is possible. The customized shield would be shaped in order to avoid under dosing. One of the objectives of radiotherapy is to achieve dose homogeneity ( 25% ) to tumor without excessively irradiating normal tissues. However, depending on the extent of disease lateral to the midline of the patient’s pelvis, the potential for inadequate dosing exists. Hence, further studies, including three dimensional treatment planning may be indicated concerning the fabrication of the midline shield for patients with invasive cervical carcinoma.
DOSIMETRIC EVALUATION OF LEAD AND TUNGSTEN SHIELDS IN ELECTRON BEAM TREATMENT
EYE
Almon S. Shiu, Ph.D.,* Samuel S. Tung, M.S.,* Robert J. Gastorf, MS.,* Kenneth R. Hogstrom, Ph.D.,* William H. Morrison, M.D.** and Lester J. Peters, M.D.** *Department of Radiation Physicis and **Department Clinical Radiotherapy, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030
of
International Journal of Radiation Oncology, Biology, Physics. Volume 35. Number 3, June 1996 This article describes the inadequate protection provided by commercially available eye shields designed for orthovoltage x-rays and used for treating with electron beam energies equal to or greater than 6 MeV. A similar eye shield constructed of tungsten was designed and fabricated. The advantages of this shield over the lead shield were discussed. An eye phantom was designed and built of nontransparent polystyrene to simulate the shape of an eyeball. Electron transmission measurements of the eye shields were made using x v-2 film. One film each with and without the eye shield was exposed for each electron beam energy. None of the commercially available lead eye shields covered with plastic coating offered sufficient protection for 6 MeV electrons. To adequately block 6 MeV and 9 MeV electrons, the resulting eye shields are too thick to fit under the eyelid. As for the tungsten eye shield, a thickness of approximately 3 mm. of tungsten would adequately block 9 MeV