Study of Variation of dose Due to Interfraction Organ Movement in Interstitial Brachytherapy: A Single Institute Experience
Introduction: Concurrent chemo-radiation is the main treatment in locally advanced cervical cancer. The change of bladder and rectum volume may lead to change in the positions of these structures and target volume during MUPIT implant which may lead to variation in dose to the organ at risk and target.
Materials and Methods: Ten patients of gynecological malignancy were included. MUPIT template was positioned under anesthesia. CT scan was done for the contouring of bladder, rectum, and target and for planning purpose which generates plan (P1). CT scan was repeated before the third fraction of the treatment (CT2). The resultant plan (P2) was analyzed qualitatively and quantitatively.
Results: Bladder volume variations of 88.18% to -68.15% were noted. This change in volume lead to differences in the maximum dose in bladder between fractions. The maximum dose variation ranged from 62.53% to -21.49%. The rectal volume variation ranges 11.71% to -46.20% due to the rectal filling. High variation in maximum dose to the rectum were observed which might be due to rectal filling. CTV volume is increased by 19.48% while in other by 19.05% and in all other patients the volume is decreased. CTV volume maximum decreased by 30.54% which might be due to decrease in edema developed during procedure. The volume variation in CTV is in range of19.48% to -30.54%.
Conclusion: It is proposed that re-planning using repeat CT scan is required before third fraction implementation.