Three-dimensional image-based high-dose-rate interstitial brachytherapy for vaginal cancer

To evaluate dosimetric and clinical outcomes of three-dimensional (3D) image-based high-dose-rate (HDR) interstitial brachytherapy (HDRB) in patients with vaginal cancers.

Thirty patients with vaginal cancers were treated with HDRB using Syed-Neblett template. CT scan was done after placement of needles for confirmation of placement and treatment planning. The target volume and organs at risk, including clinical target volume (CTV), rectum, bladder, and sigmoid colon, were contoured on CT scans. Twenty-eight (93.3%) patients received external beam radiation therapy at a median 45 (24.0-50.4)Gy in 12-28 fractions, followed by HDRB at 3.75-5.0Gy per fraction in five fractions. Total doses for CTV and organs at risk from external beam radiation therapy and HDRB were summated and normalized to a biologically equivalent dose of 2Gy per fraction.

Seventeen patients (56.7%) with primary vaginal cancer and 13 patients (43.3%) with recurrent vaginal cancers were treated with 3D HDRB. The mean CTV was 39.3±25.7 cm(3), and the median tumor diameter was 3.3 (1.3-8.0)cm. The median biologically equivalent dose of 2Gy per fraction for 2cc of bladder, rectum, and sigmoid was 55.0, 56.3, 50.0Gy, respectively. The median D(90) for high-risk CTV was 74.3 (36.3-81.1)Gy. The mean volume receiving 100%, 150%, and 200% of prescribed dose was 90.7±10.0%, 41.3±14.6%, and 17.7±8.3%, respectively. With a median followup of 16.7 months, the respective 1-/2-year locoregional and overall survival rates were 84.4%/78.8% and 82.1%/70.2%, respectively. There were no Grade ≥3 gastrointestinal complications. Late complications of Grade 3 vaginal ulceration and Grade 4 vaginal necrosis were seen in two cases.

Initial results of 3D HDRB using our fractionation schedule in the treatment of vaginal cancers showed good local response with acceptable morbidities.