Analysis of interfractional variations of bladder volume along the course of Prostate irradiation

Background: Pelvic irradiation is used for early stages or locally advanced pelvic tumors as cervical, endometrial or prostatic cancers The bladder is a muscular hollow organ that expand and contract on daily basis, change in size during radiotherapy course along with displacement of adjacent organs is a major challenge for accurate dose delivery The variations in bladder volume through the course of treatment is observed [3] Methods: A cross-section study was conducted in International Medical Center in Egypt in 2022 including a total of 20 patients with localized prostate cancer and planned for radiotherapy and a total of 5 CBCT for each patient were selected and registered to planning system for delineation of organs at risk and dosimetry calculation done on the same original plan to be a representative of the change in volumes and dose to organs at risk and the change in target coverage during the course of treatment Results : There was a decline in the mean bladder volume generally along the course of treatment, the mean bladder volume was 210.98CC in the plan CT versus 196 ml, 196 ml, 215 ml , 198 ml, 202 ml in CBCT consecutively , However, there was no significant change in dosimetry of Target volume or organs at risk Conclusion: In comfortable bladder protocol Inter-fractional variation in pelvic organs was not significant and didn’t make significant change to target volume coverage or violate dose constraints of organs at risk