Surface mould brachytherapy in oral and oropharyngeal cancers

Introduction
There are insufficient data on surface mold brachytherapy (SMB) in treating oral cancers. We reviewed our institutional experience to investigate the efficacy and toxicity of this treatment modality.

Material and methods
We retrospectively reviewed all the patients treated between 1989 and 2018 with high-dose-rate iridium-192 SMB for oral and oropharyngeal squamous cell carcinomas at our institution. Surface mold brachytherapy was delivered via an acrylic surface mold with 1–5 inserted catheters spaced 1 cm apart fabricated by our dental oncologist. The Kaplan-Meier product estimator was used to assess local control (LC), locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS). Cox proportional hazards regression analysis was used to assess the relationship of various variables and patient outcomes.

Results
Eighteen patients met the inclusion criteria and were evaluated. Indications for treatment were primary tumor (n = 13), local recurrence (2), locoregional recurrence (1), and oligometastatic disease (1). Ten patients received SMB alone and 8 received external beam radiotherapy with an SMB boost. The acute toxicity outcomes were as follows: no toxicity (n = 1), grade 1 (7), grade 2 (9), and grade 3 (1). Late effects were rare, only occurring in 3 patients. The one- and two-year LC were 81% and 68%, LRC 77% and 64%, DMFS 81% and 81%, and OS 77% and 46%.

Conclusions
Surface mold brachytherapy is a viable modality as either primary or boost treatment for superficial oral cancers. In our patients, this treatment method has a low toxicity profile and resulted in reasonable LC.