Dosimetric Evaluation of OARs from SAVE Protocol. Journal Article

Authors: Kunz, JN; Huang, YJ; Casper, AC; Suneja, G; Burt, LM; Jhingran, A; Joyner, MM; Harkenrider, MM; Small, W; Grant, JD; Kidd, EA; Boucher, K; Gaffney, DK
Article Title: Dosimetric Evaluation of OARs from SAVE Protocol.
Abstract: PURPOSE: To evaluate dosimetric characteristics to organs at risk from short course adjuvant vaginal cuff brachytherapy (VCB) in early endometrial cancer compared to standard of care in a multi-institutional prospective randomized trial. METHODS AND MATERIALS: SAVE is a prospective, phase III, multisite randomized trial where 108 patients requiring VCB were randomized to an experimental short course arm (11 Gy x 2Fx to surface) and standard of care arm (SOC). Those randomized to the SOC arm were subdivided into treatment groups based off of treating physician discretion as follows: 7 Gy x 3Fx to 5mm, 5-5.5 Gy x 4Fx to 5mm, and 6 Gy x 5Fx to surface. In order to evaluate doses to OARs of each SAVE cohort, the rectum, bladder, sigmoid, small bowel, and urethra were contoured on the planning CT and doses to OARs were compared by treatment arm. Absolute doses for each OAR and from each fractionation scheme were converted to 2 Gy equivalent dose (EQD2). Each standard of care arm was compared to the experimental arm separately using a one-way analysis of variance, followed by pairwise comparisons using Tukey's Honest Significant Difference (HSD) test. RESULTS: The experimental arm had significantly lower doses for rectum, bladder, sigmoid, and urethra when compared to the 7 Gy x3 and 5-5.5 Gy x4 fractionation schemes; however, the experimental arm did not differ from the 6 Gy x5 fractionation scheme. For small bowel doses, none of the SOC fractionation schemes were statistically different than the experimental. The highest EQD2 doses to the examined OARs were observed to come from the most common dose fractionation scheme of 7 Gy x 3Fx. With a short median follow up of one year, there have been no isolated vaginal recurrences. CONCLUSIONS: Experimental short course VCB of 11 Gy x 2Fx to the surface provides a comparable biologic effective dose to standard of care courses. Experimental short course VCB was found to reduce or be comparable to D2cc and D0.1cc EQD2 doses to rectum, bladder, sigmoid, small bowel, and urethra critical structures. This may translate into a comparable or lower rate of acute and late side effects.
Journal Title: International journal of radiation oncology, biology, physics
ISSN: 1879-355X; 0360-3016
Publisher: Elsevier Inc  
Date Published: 2023