Pulse-dose-rate interstitial brachytherapy in anal squamous cell carcinoma: clinical outcomes and patients' health quality perception

Purpose: To examine clinical outcomes and quality of life of patients with anal squamous cell carcinoma treated with interstitial pulsed-dose-rate brachytherapy (PDR-BT) with a boost to residual tumor after external radiotherapy. Material and methods: Medical records of patients receiving a brachytherapy boost after radiotherapy for anal squamous cell carcinoma in our Institute between 2008 and 2019 were retrospectively reviewed. After receiving pelvic irradiation +/- concurrent chemotherapy, patients received PDR-BT boost to residual tumor, in order to deliver a minimal total dose of 60 Gy. Patients' outcomes were analyzed, with primary focus on local control, sphincter preservation, morbidity, and quality of life. Results: A total of 42 patients were identified, included 24, 13, and 5 patients with I, II, and III tumor stages, respectively. Median brachytherapy (BT) dose was 20 Gy (range, 10-30 Gy). Median dose per pulse was 42 cGy (range, 37.5-50 cGy). With median follow-up of 60.4 months (range, 5.4-127.4 months), estimated local control and colostomy-free survival rates at 5 years were both 88.7% (95% CI: 67.4-96.4%). The largest axis of residual lesion after external beam radiation therapy (EBRT) and poor tumor shrinkage were associated with more frequent relapses (p = 0.02 and p = 0.007, respectively). Out of 40 patients with more than 6 months follow-up, only one experienced severe delayed toxicity (fecal incontinence). Health quality perception was very good or good in 20 of 22 (91%) patients, according to their replies of quality-of-life surveys. A total dose >= 63 Gy was associated with higher number of anorectal grade 1+ toxicities (n = 1.5 vs. n = 0.61, p = 0.02). Conclusions: In this cohort of 42 patients with mainly I and II tumor stages, PDR-BT boost allowed for local control in 88.7% of patients, with only one grade 3 anorectal toxicity.