A comparison between 2D and 3D planning of high-dose-rate vaginal cuff brachytherapy in patients with stage I-II endometrial cancer using cobalt-60

Purpose: Post-surgery radiation can reduce the risk of loco-regional relapse in high-intermediate-risk endometrial cancer. High-dose-rate vaginal cuff brachytherapy (HDR-BRT) is an acceptable method of radiation in majority of en-dometrial cancer cases. Although 2D planning is frequently used for treatment based on physical examination without any imaging, measurement of the dose received by organs-at-risk (OARs) is not possible. Therefore, the present study was the first to compare dose delivered to target and OARs in 2D vs. 3D planning in patients treated with cobalt-60 source. Material and methods: In this study, organs including vagina wall, bladder, rectum, and sigmoid were contoured on computed tomography (CT) scan images of 37 endometrial cancer patients, and doses delivered to organs were recorded. Statistics, such as D-90, D-99, V-100, V-150, V-200, D-0.1cc, D-1cc, and D-2cc were determined. Results: D-90 and D-99 were lower in 3D treatment planning in comparison with 2D. Although V-100 was more in 3D planning, V-150 and V-200 were less. Analyzing D-0.1cc, D-1cc, and D-2cc of OARs revealed that doses given to rectum, sigmoid, and bladder were less in 3D planning compared to 2D. Conclusions: Comparison of 2D and 3D planning results showed that 3D planning could deliver an appropriate dose to the target while sparing more OARs.