Vaginal cuff brachytherapy: do we need to treat to more than a two-centimeter active length?

PURPOSE: American Brachytherapy Society (ABS) guidelines recommend using a 3-5 cm active length (AL) when treating vaginal cuff (VC) in adjuvant setting of endometrial cancer (EC). The purpose of this study was to evaluate local control and toxicity, using an AL of 1 or 2 cm and immobilization with a traditional table-mounted (stand) or patient-mounted (suspenders) device. MATERIAL AND METHODS: Between 2005 and 2019, 247 patients with EC were treated with adjuvant high-dose-rate vaginal cuff (HDR-VC) brachytherapy with or without external beam radiation (EBRT). Treatment was prescribed to a 0.5 cm depth, with an AL of 1 or 2 cm, using stand or suspenders. VC boost after EBRT was typically administered with 2 fractions of 5.5 Gy, while VC brachytherapy alone was typically applied with 3 fractions of 7 Gy or 5 fractions of 5.5 Gy. RESULTS: The combination of suspender immobilization and an AL of 2 cm (n = 126, 51%) resulted in 5-year local control of 100%. An AL of 2 cm compared to 1 cm correlated with better local control (99.1% vs. 88.5%, p = 0.0479). Regarding immobilization, suspenders correlated with improved local control compared to stand (100% vs. 86.7%, p = 0.0038). Immobilization technique was significantly correlated with AL (p < 0.0001). Only 5 (2.0%) patients experienced grade ≥ 3 toxicity, all of whom received EBRT. CONCLUSIONS: In the present series, an AL of 2 cm provided excellent local control, while 1 cm was inadequate. Suspender immobilization was a practical alternative to stand immobilization in HDR brachytherapy of the vaginal cuff.