Influence of Bladder Volume on the Dose to the Target and Organs at Risk in High Dose Rate Intracavitary Brachytherapy of Cervix

Aim The aim of this study is to report the influence of bladder volume on the dose to the target and OAR in CT-based high dose rate intracavitary brachytherapy of cervix and to determine the optimal bladder volume required during intracavitary brachytherapy. Materials and Methods A total of 100 CT datasets of cervical cancer patients were taken up for analysis. The volumes of the target and the organs at risk were contoured. Dose volume histograms were generated and the dose to 0.1 cc, 1 cc and 2 cc of bladder, rectum and sigmoid and dose received by 90% of the clinical target volume were recorded. CT datasets were divided into two cohorts-bladder volume less than 70 ml and bladder volume more than 70 ml and the differences in dosimetry were computed. Results Fifty-three applications with bladder volume less than 70 ml and 51 applications with bladder volume more than 70 ml were analyzed. Volume of bladder filling did not have a significant impact on the dose delivered to 0.1 cc, 1 cc and 2 cc of bladder (p value= 0.87, 0.45, 0.19, respectively). The dose to the rectum was significantly lower when the bladder volume was less than 70 ml. (p value = 0.016, 0.008 and 0.003, respectively). Bladder distension did not significantly affect the dose delivered to the sigmoid or D90CTV. Conclusions Bladder volume more than 70 ml had a significant impact on the rectal dosimetry in our study. Bladder volume did not affect the dose to the other organs at risk and the target. Based on our study results, we conclude that the bladder volume should be less than 70 ml in order to avoid more doses to the rectum.However, we need to analyze a larger cohort of patients to derive any finite conclusions.