Dosimetric Impact of Bladder Volumetric Changes During Helical Radiotherapy for Rectal Cancer

Introduction: This study aims to investigate the dosimetric impact of bladder volumetric changes during helical radiotherapy (RT) for rectal cancer (RC).Material and Methods: A total of ۴۲ RC patients' helical RT treatment plans were analyzed. The bladder volumes were divided into ۳ groups (Group۱: V<۱۰۰ml, Group۲ ۱۰۰ml≤V≤۲۰۰ml, and Group۳V>۲۰۰ml). Planning target volume (PTV), PTV boost, bladder, bowel, right, and left femoral head dose values were analyzed and compared between groups. Statistical analysis was done with a one-way ANOVA test in SPSS۱۸.۰ program. A value of p <۰.۰۵ was considered statistically significant.Results: The median age of the patients was ۵۹ (range:۲۲-۸۷) and bladder volume ranged from ۴۱.۴۴ml-۶۲۰.۸۲ml. In the dosimetric data comparison of the patient groups with different bladder volumes, the D۵۰ dose values of PTV and PTV boost volume was highest in Group ۳ (p=۰.۰۳۹). No statistical significance was found between PTV and PTV boost’ doses of D۹۸ and D۲ ​​and groups. The optimum PTV dose value was in Group۲. Bowel doses were highest in Group ۱. As the bladder volume increased, the Dmax, Dmean, V۱۵%, and V۳۰% values of the bowel doses decreased. There was a statistically significant relationship between bladder Dmax doses and groups (p = ۰.۰۲۴). Femoral heads doses increased in proportion to increasing bladder volume groups and these results were statistically significant for V۵% and V۳۰% (p <۰.۰۵).Conclusion: In our study, as the bladder volume increased, there was an inversely proportional decrease in the bowel doses and a directly proportional increase in the femoral head and bladder doses. Bladder volume values significantly affected values of the target and critical organs dose during helical RT for RC

Keywords:

Bladder volume , Dosimetric Impact , Helical radiotherapy , Rectal Cancer