Impact of Vaginal Dilator Use and 68 Gy EQD2(α/β=3) Dose Constraint on Vaginal Complications in External Beam Irradiation Followed by Brachytherapy in Post-Operative Endometrial Cancer

Abstract

Background: This study evaluated the clinical outcomes of applying a 68 Gy EQD2(α/β=3) dose constraint to the most exposed 2 cm3 area of the vagina in post-operative endometrial cancer patients treated with vaginal-cuff brachytherapy after external beam irradiation and the impact of vaginal dilator use on late vaginal complications. Material and methods: We analyzed 131 patients treated with vaginal-cuff brachytherapy after external beam irradiation. Group-1 (65 patients) received one fraction of 7 Gy, and Group-2 (66 patients) received one fraction of between 5.5 and 7.0 Gy after applying a 68 Gy EQD2(α/β=3) dose constraint. Vaginal-cuff relapse, late toxicity, clinical target volume, vaginal dilator use, D90, and EQD2(α/β=3) at 2 cm3 of the most exposed part of the clinical target volume were evaluated. Descriptive analysis, the chi-squared test, Student’s t-test, and the Cox proportional and Kaplan–Meier models were used for the statistical analysis. Results: With a median follow-up of 60 months, the vaginal-cuff relapse rate was 1/131 (0.8%). Late vaginal complications appeared in 36/65 (55.4%) Group-1 patients and 17/66 (25.8%) Group-2 patients (p = 0.003). Multivariate analysis showed that belonging to Group-1 and vaginal dilator use of <9 months were independent prognostic factors of late vaginal complications with hazard ratios of 1.99 (p = 0.021) and 3.07 (p = 0.010), respectively. Conclusions: A 68 Gy EQD2(α/β=3) constraint at 2 cm3 of clinical target volume and vaginal dilator use of ≥9 months were independent prognostic factors, having protective effects on late vaginal complications.