Adjuvant Vaginal Cuff HDR Brachytherapy Prescribed to an Active Length of Two Centimeters Using Suspender Immobilization: A Baylor Scott & White Experience

Abstract

Following hysterectomy for endometrial and cervical cancer, recurrence is common in the vaginal cuff. The American Brachytherapy Society recommends prescribing to an active length (AL) of 3-5 cm (AL) with vaginal cuff brachytherapy (VCB) following hysterectomy (Gaffney D, et al. Brachytherapy 2012). The most common fixed and fractional length prescriptions in endometrial cancer are 4 cm or the proximal half of the vagina, respectively (Small W Jr, et al. Brachytherapy 2016). Length of vagina irradiation is associated with toxicity (Smeds AC et al. Int J Radiat Oncol BIol Phys 1990). The purpose of this study is to evaluate the efficacy in terms of local control and toxicity using 2 cm AL prescription during VCB following hysterectomy using patient mounted straps for immobilization. Between September 2015 and January 2019, 66 patients with endometrial (n=60) or cervical (n=6) cancer were treated with high dose-rate VCB to an AL of 2 cm prescribed to 0.5 cm depth using custom in-house patient-mounted straps for immobilization. Mean follow-up was 27 months (6-79 months). Twenty-eight percent of endometrial cancer patients were stage IA; IB, 33%; II, 13%; III, 22%; IV, 3%. Cervical cancer was mostly stage IB. Endometrial pathology included: adenocarcinoma, 57%; papillary serous/clear cell carcinoma, 28%, sarcoma, 15%. Associated grades included: I, 7%, II, 27%, and III, 67%. Cervical pathology was mostly squamous and grade III. The patients received different fractionation schedules and total doses, which were converted to BED2 using the L/Q model. VCB was typically prescribed as a single modality to 2100 cGy at 700 cGy per fraction (n=18) with a mean BED2 of 30 Gy (range, 30-31 Gy). Forty-one (68%) endometrial and 6 (100%) of cervical cancer patients received external beam to the pelvis (XRT) using a dose of 4500-5040 cGy. VCB boost was typically prescribed to 1100 cGy at 550 cGy per fraction (n=33) with a mean total BED2 to the vaginal cuff of 54 Gy (range, 54-69 Gy). There were no vaginal cuff failures. One patient experienced likely dropped metastasis at the vaginal introitus 10 months after completion of brachytherapy. Vaginal cuff recurrence-free survival (VcRFS) and vaginal recurrence-free survival (VRFS) at 3 years were 100% and 98%, respectively. With regards to vaginal toxicity, in the XRT+VCB group: one patient (2%) developed acute grade ≥2 toxicity and two patients (4%) developed chronic grade 1 toxicity. In the VCB only group, no patients experienced grade ≥2 toxicities. Three (16%) and 1 (5%) patients experienced acute and chronic grade 1 toxicity, respectively. Limiting the AL to 2 cm while using custom in-house patient mounted straps for immobilization results in minimal toxicity and excellent local control.