Can we shorten the overall treatment time in postoperative brachytherapy of endometrial carcinoma? Comparison of two brachytherapy schedules

Purpose: To analyze vaginal-cuff relapses (VCR) and toxicity of two brachytherapy (BT) schedules in postoperative endometrial carcinoma and to correlate vaginal toxicity with vaginal-surface-EQD2Gy₃ dose (VS-EQD2Gy₃). Methods/materials: 319 patients (p) I–IIIC-Figo-stage were treated with 2 BT schedules. One schedule included 166p (Group-1) to whom 3 fractions (Fr) of 4–6 Gy per week (w) of BT were administered after external beam radiotherapy (EBI) (125p) and 6Fr/2w of 4–6 Gy in exclusive-BT (41p). The second schedule included 153p (Group-2) with BT administered daily with 2Fr/w of 5–6 Gy after EBI (94p) and 5–6 Gy/4Fr/w in exclusive-BT (59p). Doses were prescribed at 5 mm from the vaginal surface. Toxicity was evaluated using RTOG scores for the rectum and bladder and objective LENT-SOMA scores for the vagina. Statistics: Chi-square, Fisher and Student's-t tests. Results: Mean follow-up (months): Group-1: 66.55 (7.73–115.40), Group-2: 41.49 (3.13–87.90). VCR: Group-1: 3p (1.88%); Group-2: 2p (1.3%). No differences were found between the two schedules comparing rectal (p = 0.170), bladder (p = 0.125) and vagina (p = 0.680) late toxicities and comparing vagina EBI + BTp vs. exclusive-BTp (p = 0.667). Significant differences in VS-EQD2_3Gy were observed considering EBI + BT (Groups 1 + 2) vs. exclusive-BT (Groups 1 + 2) (p < 0.0001); nevertheless, no association was found between VS-EQD2_3Gy and vaginal complications. Conclusions: No differences were found between the two schedules. No association was found between vaginal toxicity and VS-EQD2_3Gy. Consequently, treatment with the least number of fractions is preferable