2364 - Effect of Different Bladder Water Injection Volumes on Target Area Dose and OAR in 129 Cases of Radical Cervical Cancer Treated with Intracavitary Brachytherapy: A Real-World Study
J. Ma1, and F. Bai2; 1Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University., Xi’an, shaanxi, China, 2Department of Radiation Oncology, Xijing Hospital, Fourth Military Medical University, xian, Shaanxi, China
Purpose/Objective(s): There is no uniform standard for optimal bladder water injection volume during intracavitary brachytherapy for cervical cancer. In this study, the differences of radiation doses to the target volume and organs at risk under different bladder injection volumes were analyzed to provide a reference for determining the clinical optimal bladder volume. Materials/
Methods: This study retrospectively analyzed 129 consecutive cervical cancer patients who received brachytherapy from January 2017 to June 2022 in our center. All patients had completed whole pelvic irradiation 45-50.4GY/25-28F by 3D-CRT or volumetric modulated arc therapy/VMAT technique, and intracavitary brachytherapy was intended to be 32-35Gy/4-5F. The patient was placed with an indwelling catheter followed by an intracavitary applicator. The bladder was then emptied and filled with a dose of saline, followed by a CT scan. Different volumes of 90 ml, 110 ml, 130 ml, 160 ml, 180 ml, 200 ml, and 240 ml of saline were injected, depending on the amount of water the patient could tolerate. Differences in dose to the target area and to the organs at risk in different bladder filling states were assessed according to the precision radiation medicine system. The results were statistically analysed by one-way ANOVA or chi-square test using statistical software, and the difference was statistically significant with a P value <0.05. Results: A total of 12 patients were injected with 90 ml of water to the bladder, 30 patients were injected with 110 ml of water to the bladder, 17 patients were injected with 130 ml of water, 32 patients were injected with 160 ml of water, 9 patients were injected with 180 ml of water, 13 patients were injected with 200 ml of water, and 16 patients were injected with 240 ml of water. There was no statistically significant difference between the seven groups of patients with regard to age, intestinal preparation, tumour stage and size, and irradiation technique. Dose difference analysis showed that there was no statistically significant difference between the groups in the dose of rectal D2cc, small bowel D2cc, and HR-CTV D90, but there was a statistically significant difference in bladder D2cc and sigmoid colon D2cc. The dose (Gy) of bladder D2cc was 79.2±3.02 for 90 ml , 81.37±1.5 for 110 ml , 80.25±2.89 for 130 ml, 78.93±1.6 for 160 ml, 81.04±1.46 for 180 ml, 82.1±2.47 for 200 ml, and 81.38±1.6 for 240 ml (P<0.001) ;The dose of sigmoid colon D2cc in each group was 65.48±2.7 vs 64.12±3.9 vs 65.32±3.1 vs 63.63±3.3 vs 66.6±1.65 vs 65.5±3.43 vs 66.9±3.4 (P=0.021). Conclusion: Bladder injection volume of 90-240 ml of water in intracavitary brachytherapy for cervical cancer can meet the clinical dose requirements for the target area and organs at risk. The bladder injection of saline 160 ml can significantly reduce the maximum dose received by the bladder and the sigmoid colon, and has a certain protective effect on the bladder and the sigmoid colon. However, due to the small sample size, the results need to be verified by further expanding the sample size.