The efficacy of iodine-125 interstitial brachytherapy for the treatment of locally advanced adenoid cystic carcinoma of the base of tongue: a non-surgical approach

Introduction
The present study retrospectively evaluated the effectiveness and safety of iodine-125 interstitial brachytherapy for treatment of primary locally advanced adenoid cystic carcinoma (ACC) of the base of tongue (BOT).

Material and methods
This study was a retrospective analysis of data of 19 patients with ACC, who were treated with iodine-125 interstitial brachytherapy between March 2008 and April 2018. Overall survival (OS), disease-free survival (DFS), local control (LC), and radiation-related toxicities were determined. Factors affecting the outcomes were evaluated.

Results
Six males and 13 females were included in our study, with a median follow-up time of 35 months. 3- and 5-year OS rates were 71.5% and 47.6%, respectively. 3- and 5-year LC rates were 88.5% and 34.5%, respectively. 3- and 5-year DFS rates were 54.7% and 21.9%, respectively. A significant difference was observed in patients with or without brain metastases for OS rate. No severe acute toxicity was observed, while severe late toxicity was observed in one patient.

Conclusions
The results suggest that iodine-125 interstitial brachytherapy is an effective and safe option for the treatment of primary locally advanced ACC of the base of the tongue, with reasonably satisfactory LC and OS.