Program Information
Influence of Bladder Filling Status On Inter-Fractional Target Variation in Bladder Cancer Radiotherapy
Y Ji*, J Kwak , C Jeong , B Cho , K Chang , Y Kim , S Lee , Radiation Oncology Department, Asan Medical Center, Seoul, Korea
Presentations
SU-I-GPD-J-31 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: In radiotherapy for bladder cancer cases, the target volume and position should be maintained on daily basis. In this letter, two different bladder filling protocols were compared to examine the inter-fractional target variation.
Methods: Eight bladder cancer cases were enrolled in this study. To maintain the inter-fractional variation of bladder, the bladder voiding for initial course and the bladder filling for RF course were applied before treatments. To delineate a bladder contour of each fraction, we employed CBCT guidance images, which were acquired weekly in initial course and daily in RF course, respectively. With the CBCT contours, dice similarity coefficients (DSC) were calculated for the bladder volumes of simulation CT. Bladder portion for each fraction was defined as the relative ratio of CBCT bladder volume inside the planning bladder volume of simulation CT, while normal tissue ratio of the planning bladder volume in each fraction was indicated as a normal tissue portion.
Results: Analysis was performed with 16 planning CTs and 103 CBCTs. It was apparent in images that the bladder in RF course was more stable than initial course’s. In the comparisons between initial and RF for bladder volume, bladder portions, and normal tissue portion , the bladder volume in RF course were about 200 cc larger than those in initial. While the difference in normal tissue potion was not significant, the bladder portions in RF course were clearly bigger than bladder portions for initial course.
Conclusion: It was suggested the bladder filling using 250 cc of saline was beneficial to obtain the stable localization of bladder without any more normal tissue involvement, even if the bladder volume was bigger. It would provide the opportunity to maintain or improve target coverage.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2014R1A1A2058154)
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