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The lack of impact of pelvic irradiation on small bowel mobility: Implications for radiotherapy treatment planning
Int. J. Radiation
Oncology
Biol.
Phys.,
Pergamon
Vol. 32, No. 5, pp. 1473-1475. I995 Copyright 0 1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0360-3016/95 $9.50 + .OO
0360-3016(95)00578-S
0 Technical
Innovations
and Notes
THE LACK OF IMPACT MOBILITY: IMPLICATIONS
OF PELVIC IRRADIATION FOR RADIOTHERAPY
ON SMALL BOWEL TREATMENT PLANNING
JEFFREY C. ACKER, M.D. AND LAWRENCE B .MARKS, M.D. Duke University Medical Center, Durham, NC Purpose: Small bowel contrast is frequently used during simulation for patients undergoing pelvic radiotherapy to assist in the design of blocks that exclude small bowel from the radiation field. In many instances, a large field is treated to 45 gray (Gy), followed by a field reduction to exclude the small bowel. This prospective study was designed to assess whether the position and mobility of the small bowel changed after the initial 45 Gy, thereby determining whether a special small bowel series done at initial simulation is applicable at the time of field reduction. Methods and Materials: Twelve patients undergoing pelvic irradiation were given small bowel contrast for their initial simulation. Radiographs were taken with the bladder empty and the bladder full. The location of the small bowel and its displacement with bladder distention was measured. This entire procedure was repeated prior to field reduction (after 39.6-46.0 Gy). Results: There was no demonstrable alteration in small bowel mobility after 39.6-46.0 Gy. The approximate position of the small bowel relative to bony landmarks was unchanged. Conclusion: The position and mobility of the small bowel appears not to be affected by 39.6-46.0 Gy of pelvic radiotherapy. Therefore, it is reasonable to design reduced pelvic fields to exclude the small bowel based on special small bowel series done at initial treatment simulation. Small bowel mobility,
Radiotherapy
treatment
planning,
INTRODUCTION
Special
small bowel series.
between the time of simulation and time that the reduced field is actually treated. To addressthis issue, we herein review our experience with 12 patients who underwent small bowel imaging prior to and following pelvic radiotherapy to assesswhether or not the mobility and position of small bowel changes during this time.
Minimizing the volume of nontargeted tissue included within the radiation treatment field is a cornerstone of modem external beam radiation therapy. For patients receiving pelvic radiotherapy, portions of the small bowel are often incidentally included within the radiation treatment fields. Various maneuvers, such as treating patients in a variety of positions (2, 4, 5), on a belly board (8), or with a full bladder (6), have been used to displace the small bowel from the treatment volume (6). For a variety of pelvic tumors, it is common for the patient to receive 45 Gy to a “large” pelvic field, followed by an additional dose to a reduced volume that excludes the small bowel (3, 6, 9). One way of facilitating the exclusion of small bowel from the treatment field is to have the patient drink contrast prior to the simulation, such that the small bowel can be visualized on the simulator fields (1, 4-7). This practice assumes,however, that the position and mobility of the small bowel does not change during the 5 weeks
METHODS
AND MATERIALS
Twelve patients with a variety of pelvic tumors (prostate-6; colorectal-4; cervix- 1; bladder- 1) who were to receive “large” pelvic fields followed by reduced fields were studied. Each patient underwent two simulation procedures, one at the initiation of the “large” field and a second after 39.6-46.0 Gy (median = 45.0 Gy, mean = 43.6 Gy), delivered in 25-49 days (median = 35 days) at 1.8-2 Gy per daily fraction. Treatment was delivered with anterior-posterior/posterior-anterior (AP/ PA) fields or a four-field “box” technique. The field sizes
Reprint requeststo: Jeffrey C. Acker, M.D., Departmentof RadiationOncology, Box 3085, Duke University Medical Center, Durham, NC 27710. Acknowledgements-Dr. Marks is the recipientof an American CancerSociety CareerDevelopmentAward (#92-53). The au-
thors thank JeanneForestand JaneHoppenworthfor assistance in the preparationof this manuscript. Accepted for publication 27 October 1994.
1473
1474
I. J. Radiation Oncology 0 Biology 0 Physics
ranged from 8 X 8.5 to 17 x 26 (width x length) for the anterior and posterior fields, and 8 x 8 to 15 x 26.5, for the lateral fields. The mean field sizes were 13.5 x 13.8 for the AP/PA, and 11.7 X 13.8 for the laterals. At both simulations, small bowel contrast was given and a Foley catheter was placed. Anterior-posterior and lateral radiographs were taken with the bladder containing approximately 60 cc of liquid and again containing approximately 300 cc of liquid. The vertical displacement of the small bowel was scored. In two patients, the maneuver used to move the small bowel was the placement of the patient in the decubital position. For these two, the small bowel displacement was measured in the right to left, rather than in the superior to inferior, direction. An estimate of the volume of small intestine included within the initial pelvic field was made from the initial simulator films by taking the product of the three orthogonal dimensions of the small bowel included within the field.
RESULTS The results are shown in tabular form in Table 1. As shown, there was minimal change in the vertical displacement of the small intestine between the two simulations. The relative position of the small bowel relative to bony landmarks was essentially unchanged. The large variation noted in one patient (No. 1) was due to inadvertent underfilling of the bladder during the boost simulation.
DISCUSSION This study suggeststhat the position and mobility of the small intestine does not change during the approximate 5-week interval between the initial simulation and the completion of 45 Gy pelvic radiotherapy. We had thought it theoretically possible for the radiation to acutely cause some decreasedmobility in the small bowel, perhaps due to edema/inflammation. Our results do not support this theory. Therefore, reduced fields that intentionally exclude portions of the small intestine can be designed based on information obtained at the initial simulation. This conclusion is appropriate only for patients with similar clinical situations as those studied here. For other patients, there might be some alteration in the position or mobility of the small intestine. For example, if there were a lengthy delay between the initial simulation and the start of the reduced field treatment, there might be some change. In this study, we did not seeany impact on whether or not the patient had prior abdominal surgery. Eight of our 12 patients did have prior surgery, ranging from just a few months to several years prior to the initiation of their pelvic treatment. Small bowel adhesionscan occur following surgery, which could theoretically reduce mobility of the small bowel. It is also interesting to note the variability of the mobility of the small bowel with the bladder distention and
Volume 32, Number 5, 1995
Impact
of pelvic
irradiation
on small bowel
decubital movements. In some patients, the movement was trivial, while in others there was several centimeters of displacement. This finding is in agreement with others
mobility
l J. C. ACKER
AND
L. B. MARKS
1475
(5,9) and supports the continued use of these maneuvers to decrease the volume of normal tissue that is incidentally included with radiotherapy fields.
REFERENCES 1. Brierly, J. D.; Cummings, B. J.; Wong, C. S.; McLean, M.; Cashell, A.; Manter, S. The variation of small bowel volume within the pelvis before and during adjuvant radiation for rectal cancer. Radiother. Oncol. 3 1: 1 lo- 116; 1994. 2. Caspers, R. J. L.; Hop, W. C. J. Irradiation of true pelvis for bladder and prostatic carcinoma in supine, prone or trendelenburg position. Int. J. Radiat. Oncol. Biol. Phys. 9:589-593; 1983. 3. Devereux, D. F.; Eisenstat, T.; Zinkin, L. The safe and effective use of postoperative radiation therapy in modified Astler Coller stage C3 rectal cancer. Cancer 63:2393-2396; 1989. 4. Green, N. The avoidance of small intestine injury in gynecologic cancer. Int. J. Radiat. Oncol. Biol. Phys. 9:13851390; 1983. 5. Green, N.; Iba, G.; Smith, W. R. Measures to minimize small intestine injury in the irradiated pelvis. Int. J. Radiat. Oncol. Biol. Phys. 35:1633-1640; 1975.
Gunderson, L. L.; Russell, A. H.; Llewellyn, H. J.; Doppke, K. P.; Tepper, J. E. Treatment planning for colorectal cancer: Radiation and surgical techniques and value of smallbowel films. Int. J. Radiat. Oncol. Biol. Phys. 11:13791393; 1985. Herbert, S. H.; Curran, W. J., Jr.; Solin, L. J.; Stafford, P. M.; Lanciano, R. M.; Hanks, G. E. Decreasing gastrointestinal morbidity with the use of small bowel contrast during treatment planning for pelvic irradiation. Int. J. Radiat. Oncol. Biol. Phys. 20:835-842; 1991. 8. Shanahan, T. G.; Mehta, M. P.; Bertelrud, K. L.; Buchler, D. A.; Frank, L. E.; Gehring, M. A.; Kubsad, S. S.; Utrie, P. C.; Kinsella, T. J. Minimization of small bowel volume within treatment fields utilizing customized “belly boards.” Int. J. Radiat. Oncol. Biol. Phys. 19:469-476; 1990. 9. Tepper, J. E.; Cohen, A. M.; Wood, W. C.; Orlow, E. L.; Hedberg, S. E. Postoperative radiation therapy of rectal cancer. Int. J. Radiat. Oncol. Biol. Phys. 13:5- 10; 1987.
Oncology
Biol.
Phys.,
Pergamon
Vol. 32, No. 5, pp. 1473-1475. I995 Copyright 0 1995 Elsevier Science Ltd Printed in the USA. All rights reserved 0360-3016/95 $9.50 + .OO
0360-3016(95)00578-S
0 Technical
Innovations
and Notes
THE LACK OF IMPACT MOBILITY: IMPLICATIONS
OF PELVIC IRRADIATION FOR RADIOTHERAPY
ON SMALL BOWEL TREATMENT PLANNING
JEFFREY C. ACKER, M.D. AND LAWRENCE B .MARKS, M.D. Duke University Medical Center, Durham, NC Purpose: Small bowel contrast is frequently used during simulation for patients undergoing pelvic radiotherapy to assist in the design of blocks that exclude small bowel from the radiation field. In many instances, a large field is treated to 45 gray (Gy), followed by a field reduction to exclude the small bowel. This prospective study was designed to assess whether the position and mobility of the small bowel changed after the initial 45 Gy, thereby determining whether a special small bowel series done at initial simulation is applicable at the time of field reduction. Methods and Materials: Twelve patients undergoing pelvic irradiation were given small bowel contrast for their initial simulation. Radiographs were taken with the bladder empty and the bladder full. The location of the small bowel and its displacement with bladder distention was measured. This entire procedure was repeated prior to field reduction (after 39.6-46.0 Gy). Results: There was no demonstrable alteration in small bowel mobility after 39.6-46.0 Gy. The approximate position of the small bowel relative to bony landmarks was unchanged. Conclusion: The position and mobility of the small bowel appears not to be affected by 39.6-46.0 Gy of pelvic radiotherapy. Therefore, it is reasonable to design reduced pelvic fields to exclude the small bowel based on special small bowel series done at initial treatment simulation. Small bowel mobility,
Radiotherapy
treatment
planning,
INTRODUCTION
Special
small bowel series.
between the time of simulation and time that the reduced field is actually treated. To addressthis issue, we herein review our experience with 12 patients who underwent small bowel imaging prior to and following pelvic radiotherapy to assesswhether or not the mobility and position of small bowel changes during this time.
Minimizing the volume of nontargeted tissue included within the radiation treatment field is a cornerstone of modem external beam radiation therapy. For patients receiving pelvic radiotherapy, portions of the small bowel are often incidentally included within the radiation treatment fields. Various maneuvers, such as treating patients in a variety of positions (2, 4, 5), on a belly board (8), or with a full bladder (6), have been used to displace the small bowel from the treatment volume (6). For a variety of pelvic tumors, it is common for the patient to receive 45 Gy to a “large” pelvic field, followed by an additional dose to a reduced volume that excludes the small bowel (3, 6, 9). One way of facilitating the exclusion of small bowel from the treatment field is to have the patient drink contrast prior to the simulation, such that the small bowel can be visualized on the simulator fields (1, 4-7). This practice assumes,however, that the position and mobility of the small bowel does not change during the 5 weeks
METHODS
AND MATERIALS
Twelve patients with a variety of pelvic tumors (prostate-6; colorectal-4; cervix- 1; bladder- 1) who were to receive “large” pelvic fields followed by reduced fields were studied. Each patient underwent two simulation procedures, one at the initiation of the “large” field and a second after 39.6-46.0 Gy (median = 45.0 Gy, mean = 43.6 Gy), delivered in 25-49 days (median = 35 days) at 1.8-2 Gy per daily fraction. Treatment was delivered with anterior-posterior/posterior-anterior (AP/ PA) fields or a four-field “box” technique. The field sizes
Reprint requeststo: Jeffrey C. Acker, M.D., Departmentof RadiationOncology, Box 3085, Duke University Medical Center, Durham, NC 27710. Acknowledgements-Dr. Marks is the recipientof an American CancerSociety CareerDevelopmentAward (#92-53). The au-
thors thank JeanneForestand JaneHoppenworthfor assistance in the preparationof this manuscript. Accepted for publication 27 October 1994.
1473
1474
I. J. Radiation Oncology 0 Biology 0 Physics
ranged from 8 X 8.5 to 17 x 26 (width x length) for the anterior and posterior fields, and 8 x 8 to 15 x 26.5, for the lateral fields. The mean field sizes were 13.5 x 13.8 for the AP/PA, and 11.7 X 13.8 for the laterals. At both simulations, small bowel contrast was given and a Foley catheter was placed. Anterior-posterior and lateral radiographs were taken with the bladder containing approximately 60 cc of liquid and again containing approximately 300 cc of liquid. The vertical displacement of the small bowel was scored. In two patients, the maneuver used to move the small bowel was the placement of the patient in the decubital position. For these two, the small bowel displacement was measured in the right to left, rather than in the superior to inferior, direction. An estimate of the volume of small intestine included within the initial pelvic field was made from the initial simulator films by taking the product of the three orthogonal dimensions of the small bowel included within the field.
RESULTS The results are shown in tabular form in Table 1. As shown, there was minimal change in the vertical displacement of the small intestine between the two simulations. The relative position of the small bowel relative to bony landmarks was essentially unchanged. The large variation noted in one patient (No. 1) was due to inadvertent underfilling of the bladder during the boost simulation.
DISCUSSION This study suggeststhat the position and mobility of the small intestine does not change during the approximate 5-week interval between the initial simulation and the completion of 45 Gy pelvic radiotherapy. We had thought it theoretically possible for the radiation to acutely cause some decreasedmobility in the small bowel, perhaps due to edema/inflammation. Our results do not support this theory. Therefore, reduced fields that intentionally exclude portions of the small intestine can be designed based on information obtained at the initial simulation. This conclusion is appropriate only for patients with similar clinical situations as those studied here. For other patients, there might be some alteration in the position or mobility of the small intestine. For example, if there were a lengthy delay between the initial simulation and the start of the reduced field treatment, there might be some change. In this study, we did not seeany impact on whether or not the patient had prior abdominal surgery. Eight of our 12 patients did have prior surgery, ranging from just a few months to several years prior to the initiation of their pelvic treatment. Small bowel adhesionscan occur following surgery, which could theoretically reduce mobility of the small bowel. It is also interesting to note the variability of the mobility of the small bowel with the bladder distention and
Volume 32, Number 5, 1995
Impact
of pelvic
irradiation
on small bowel
decubital movements. In some patients, the movement was trivial, while in others there was several centimeters of displacement. This finding is in agreement with others
mobility
l J. C. ACKER
AND
L. B. MARKS
1475
(5,9) and supports the continued use of these maneuvers to decrease the volume of normal tissue that is incidentally included with radiotherapy fields.
REFERENCES 1. Brierly, J. D.; Cummings, B. J.; Wong, C. S.; McLean, M.; Cashell, A.; Manter, S. The variation of small bowel volume within the pelvis before and during adjuvant radiation for rectal cancer. Radiother. Oncol. 3 1: 1 lo- 116; 1994. 2. Caspers, R. J. L.; Hop, W. C. J. Irradiation of true pelvis for bladder and prostatic carcinoma in supine, prone or trendelenburg position. Int. J. Radiat. Oncol. Biol. Phys. 9:589-593; 1983. 3. Devereux, D. F.; Eisenstat, T.; Zinkin, L. The safe and effective use of postoperative radiation therapy in modified Astler Coller stage C3 rectal cancer. Cancer 63:2393-2396; 1989. 4. Green, N. The avoidance of small intestine injury in gynecologic cancer. Int. J. Radiat. Oncol. Biol. Phys. 9:13851390; 1983. 5. Green, N.; Iba, G.; Smith, W. R. Measures to minimize small intestine injury in the irradiated pelvis. Int. J. Radiat. Oncol. Biol. Phys. 35:1633-1640; 1975.
Gunderson, L. L.; Russell, A. H.; Llewellyn, H. J.; Doppke, K. P.; Tepper, J. E. Treatment planning for colorectal cancer: Radiation and surgical techniques and value of smallbowel films. Int. J. Radiat. Oncol. Biol. Phys. 11:13791393; 1985. Herbert, S. H.; Curran, W. J., Jr.; Solin, L. J.; Stafford, P. M.; Lanciano, R. M.; Hanks, G. E. Decreasing gastrointestinal morbidity with the use of small bowel contrast during treatment planning for pelvic irradiation. Int. J. Radiat. Oncol. Biol. Phys. 20:835-842; 1991. 8. Shanahan, T. G.; Mehta, M. P.; Bertelrud, K. L.; Buchler, D. A.; Frank, L. E.; Gehring, M. A.; Kubsad, S. S.; Utrie, P. C.; Kinsella, T. J. Minimization of small bowel volume within treatment fields utilizing customized “belly boards.” Int. J. Radiat. Oncol. Biol. Phys. 19:469-476; 1990. 9. Tepper, J. E.; Cohen, A. M.; Wood, W. C.; Orlow, E. L.; Hedberg, S. E. Postoperative radiation therapy of rectal cancer. Int. J. Radiat. Oncol. Biol. Phys. 13:5- 10; 1987.