Adjuvant brachytherapy for oral squamous cell carcinomas: a single-center experience comparing low-dose and pulsed-dose-rate techniques.

Objective: This study aims to assess the outcomes of adjuvant interstitial brachytherapy (BT) to the tumor bed for oral cavity squamous cell carcinoma (SCC), and to compare the oncological outcomes and toxicity profile of low-dose-rate (LDR) and pulsed-dose-rate (PDR) BT.

Design: This retrospective single-center study included all patients who underwent postoperative LDR- or PDR-BT to the tumor bed as the sole adjuvant treatment for an oral tongue or floor of the mouth SCC between January 2000 and December 2020.

Results: A total of 79 patients were eligible for this study. The cohort was divided into an LDR group (n = 38) and a PDR group (n = 41). The median time interval between surgery and brachytherapy was 55 days. Median delivered total dose was 55 Gy and median hospital stay was 5 days. Five patients (8.3%) experienced grade 3-4 early toxicity, 2 in the LDR group and 3 in the PDR group. Late toxicities were present in 28 patients (44.4%) and were dominated by grade 1-2 residual pain and dysesthesia, without a statistical difference between the groups. After a median follow-up of 65.1 months, 5‑year local control (LC), disease-free survival (DFS), and overall survival (OS) for the whole cohort were 76.3% (95% CI = 63.4-85.1), 61.6% (95% CI = 49.0-72.0), and 71.4% (95% CI = 58.6-80.8), respectively.

Conclusion: Adjuvant BT after excision of oral cavity SCC provides satisfactory oncological outcomes along with good tolerance. In our study, PDR-BT showed similar oncological and functional results to LDR-BT in this indication.