Long-term oncologic outcomes of high-dose-rate interstitial brachytherapy (interventional radiotherapy) in oral tongue squamous cell carcinoma; 15 years of experience from a tertiary cancer center

PURPOSE: High-dose-rate interstitial brachytherapy (HDR-IBT) is commonly used for treating oral tongue squamous cell carcinoma (OTSCC). This study aims to evaluate long-term outcomes, survival predictors, chronic side effects, and failure patterns in patients receiving adjuvant HDR-IBT after surgical resection.

METHODS AND MATERIALS: We analyzed records of 239 early-stage OTSCC patients treated with surgery, and adjuvant HDR-IBT at a tertiary cancer center from October 2010 to February 2024. Follow-up included assessing survival status, disease recurrence, and chronic adverse events.

RESULTS: Among the patients, 142 received HDR-IBT as monotherapy, 73 as a boost to external beam radiotherapy (EBRT), and 24 as salvage therapy. The 5-year overall survival (OS) rates were 78.4%, 56.0%, and 53.5%, while disease-free survival (DFS) rates were 74.7%, 57.7%, and 32.6%, respectively. The monotherapy group demonstrated the best outcomes, whereas the salvage group had the poorest results. Age and T stage were independent predictors of OS, with local recurrence within 5 years linked to initial T stage in monotherapy (p = 0.057) and EBRT boost patients (p = 0.046). Chronic adverse events such as xerostomia, fibrosis, and dysesthesia were more prevalent in the salvage group compared to the other groups.

CONCLUSIONS: HDR-IBT is an effective treatment for early-stage OTSCC, yielding favorable survival rates and manageable acute and chronic side effects, particularly when used in low-risk patients for regional recurrence.

KEYWORDS: Cancer of tongue, Squamous cell carcinoma, Adjuvant radiotherapy, Brachytherapy