Brachytherapy (Interventional Radiotherapy) for Squamous Cell Carcinomas of the Nasal Vestibule: Optimization of Dose and Technique

Rationale: Primary brachytherapy (also known as Interventional Radiotherapy, IRT) achieves high cure rates in cancer of the nasal vestibule (CNV) while preserving nasal aesthetics and function. In our recently published nationwide multicenter study, brachytherapy (BT) increased nose preservation probability from 61 to 82 % compared to external beam radiotherapy (EBRT). Although late toxicity was more common following BT, it was predominantly CTCAE grade 1-2 and deemed acceptable given the substantial benefit in local control and nose preservation. However, a notable finding of our study was the substantial variation in BT practice, including implantation techniques, dose prescriptions, and treatment planning. Although this analysis covers one of the largest series of CNV patients to date, patient numbers were insufficient to reliably compare the efficacy of the different application/implantation techniques and doses. The retrospective design of the study proved inappropriate for a detailed analysis of the dose-volume data, which is necessary to correlate implantation and dose data to outcome. As the integral brachytherapy dose, as well as the dose inhomogeneity in tissue may vary widely depending on how the dose is prescribed, simple prescription doses are insufficient to characterize a brachytherapy plan comprehensively. Given the excellent disease control achieved with BT, optimizing aesthetic and functional outcomes while minimizing toxicity becomes increasingly important. Therefore, to optimize BT treatment for CNV and facilitate its wider adoption, detailed prospective data collection on treatment parameters, dose plans, toxicity (both physician-reported and patient-reported), oncological outcomes, and functional results is necessary. This study is designed as a non-comparative, descriptive prospective registry aimed at systematically documenting current international practice in brachytherapy for cancer of the nasal vestibule. Objective: To prospectively de