Small Bowel Sparing Effect of Small Bowel Displacement System in 3D-CRT and IMRT for Cervix Cancer

Kang, Min Kyu; Huh, Seung Jae; Han, Youngyih; Park, Won; Ju, Sang Gyu; Kim, Kyoung Ju; Lee, Jeung Eun; Park, Young Je; Nam, Hee Rim; Lim, Do Hoon; Ahn, Yong Chan

Abstract

PURPOSE: In radiotherapy for cervix cancer, both 3-dimensioal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) could reduce the dose to the small bowel (SB), while the small bowel displacement system (SBDS) could reduce the SB volume in the pelvic cavity. To evaluate the effect of the SBDS on the dose to the SB in 3D-CRT and IMRT plans, 3D-CRT and IMRT plans, with or without SBDS, were compared. MATERIALS AND MEHTODS: Ten consecutive uterine cervix cancer patients, receiving curative radiotherapy, were accrued. Ten pairs of computerized tomography (CT) scans were obtained in the prone position, with or without SBDS, which consisted of a Styrofoam compression device and an individualized custom-made abdominal immobilization device. Both 3D-CRT, using the 4-field box technique, and IMRT plans, with 7 portals of 15 MV X-ray, were generated for each CT image, and prescribed 50 Gy (25 fractions) to the isocenter. For the SB, the volume change due to the SBDS and the DVHs of the four different plans were analyzed using paired t-tests.
RESULTS
The SBDS significantly reduced the mean SB volume from 522 to 262 cm3 (49.8% reduction). The SB volumes that received a dose of 10~50 Gy were significantly reduced in 3D-CRT (65~80% reduction) and IMRT plans (54~67% reduction) using the SBDS. When the SB volumes that received 20~50 Gy were compared between the 3D-CRT and IMRT plans, those of the IMRT without the SBDS were significantly less, by 6~7%, than those for the 3D-CRT without the SBDS, but the volume difference was less than 1% when using the SBDS.
CONCLUSION
The SBDS reduced the radiation dose to the SB in both the 3D-CRT and IMRT plans, so could reduce the radiation injury of the SB.