A retrospective analysis to compare the dosimetric parameters of two rectum-sparing techniques during intracavitary brachytherapy with tandem-ring applicators for cervical cancer

Purpose To compare the standard International Commission on Radiation Units and Measurements-38 (ICRU-38) rectum and bladder point doses with a modified technique of combining radio-opaque vaginal packing (VP) and rectal retractor (RR) versus the conventional technique of using RR alone for rectum separation during high-dose-rate (HDR)-intracavitary brachytherapy (ICB) with tandem-ring (TR) applicators. Methods Between January 2021 and August 2022, 41 cancer patients received at least one ICB session with the conventional and at least one with the modified technique using the same applicator set and loading pattern. The remaining ICB sessions, were done using that technique, which gave the best dosimetric parameters during previous sessions in that particular patient. Results Out of total 111 ICB sessions with TR applicators, 44 constitute conventional group and 67 modified group. For the same dose (100%) prescribed to point A in both groups, the mean dose to the ICRU rectal point was 44.1% of the prescription dose (range:23.8-77.8%, median 42.5%) in modified group and 55.5% (range: 36.4-73.1%, median 56.5%) in the conventional group. There was 11.4% reduction in mean dose to the ICRU rectal point (p<0.001). The mean dose to the ICRU bladder point was 55.5% of the prescription dose (range, 14.8-127.2%; median 55.5%) in the modified group and 49.8% (range 11.6-95.6%; median 51.5%) in the conventional group. There was 5.7% increase in the mean dose to the ICRU bladder point (p=0.21). The other point doses and volume parameters were similar between groups. Conclusion Modified technique of combining rectal retractor with customised radio-opaque vaginal packing, significantly reduced the ICRU rectal point dose, compared to using a rectal retractor alone during brachytherapy with tandem-ring applicators.