Optimizing Toxicity and Local Control in Adjuvant Vaginal Cuff HDR brachytherapy: Stand vs. Suspender Immobilization and One vs. Two-centimeter Active Length Prescriptions

Abstract

Vaginal cuff recurrence is common following hysterectomy for endometrial and cervical cancer. The American Brachytherapy Society recommends prescribing to an active length (AL) of 3-5 cm (AL) with vaginal cuff brachytherapy (VCB) following hysterectomy. Treatment toxicity is associated with length of vagina irradiation. The most common fractional and fixed length prescriptions in endometrial cancer are the proximal half of the vagina or 4 cm, respectively. The purpose of this study is to evaluate the local control and toxicity of VCB using AL prescriptions of 1 or 2 cm with a traditional stand or patient-mounted straps for immobilization. Between March 2005 and January 2019, 251 patients with gynecologic cancer were treated with high dose-rate VCB. AL was 1 (52%) or 2 (48%) cm prescribed to a depth of 0.25 (10%) or 0.5 cm (90%) using a traditional stand (47%) or custom in-house patient-mounted straps (53%) for immobilization. A majority of patients immobilized with straps were treated to an AL of 2 cm (90%). Mean follow-up was 39 months (range, 3-111 months). Forty-one percent of patients were stage IA; IB, 29%; II, 6%; III, 22%; IV, 2%. Pathology included: adenocarcinoma, 73%; papillary serous/clear cell carcinoma, 18%; and other, 9%. Associated grades included: I, 14%; II, 33%; and III, 42%. VCB was most commonly prescribed as a single modality to 21 Gy in 3 fractions (37%), with a mean BED2 of 32 Gy (9.3-61 Gy). Using a dose of 45-56.2 Gy, 52% of patients received external beam radiation (XRT). VCB boost was most commonly prescribed to 11 Gy in 2 fractions (70%), with a mean total BED2 to the vaginal cuff of 62 Gy (54-83 Gy). Vaginal cuff recurrence-free survival (VcRFS) at 5 years was 99% and 89% (p = .13) using AL prescriptions of 2 vs 1 cm, respectively. VcRFS at 5 years was 100% and 88% (p = .013) using strap vs stand immobilization, respectively. In the VCB only group: 15.5%, 11.8%, and 7.5% of patients experienced grade 1-2 vaginal, bladder, rectal toxicities, respectively. Grade 1-2 toxicities in the VCB only group were: 7.2%, 17%, and 8.5% at 1 cm AL compared to 22%, 4.1%, and 2% at 2 cm AL (each to vagina, bladder, and rectum, respectively). One patient treated to an AL of 2 cm had a grade 3 toxicity (rectal). In the XRT+VCB group: 22%, 36%, and 60% of patients experienced grade 1-2 vaginal, bladder, and rectal toxicities, respectively. Four patients had a grade 3 toxicity (1 bladder and 3 rectal). Limiting the AL prescription to 2 cm results in minimal toxicity and excellent local control. Though not significantly different, our results suggest exercising caution when considering a 1 cm AL. Patients immobilized with straps had improved 100% 5-year VcRFS. Prospective trials comparing immobilization techniques and prescription length are needed.