Results of sole postoperative interstitial, high-dose-rate brachytherapy of T1-2 tongue tumours

Purpose To describe the results of treating tongue cancer patients with single postoperative interstitial, high-dose-rate (HDR) brachytherapy (BT) after resection. Methods Between January 1998 and April 2019, 45 patients with squamous cell histology, stage T1-2N0-1M0 tongue tumours were treated by surgery followed by a single HDR BT in case of negative prognostic factors (close or positive surgical margin, lymphovascular and/or perineural invasion). The average dose was 29 Gy (range: 10-45 Gy) and rigid metal needles were used in 11 (24%) and flexible plastic catheters in 34 cases (76%). Survival parameters, toxicities and the prognostic factors influencing survival were analysed. Results During a mean follow-up of 103 months (range: 16-260 months) for surviving patients, the 10-year local and regional control (LC, RC), overall survival (OS), and disease-specific survival (DSS) probabilities were 85, 73, 34 and 63%, respectively. The incidence of local grade 1, 2 and 3 mucositis was 23, 73 and 4%, respectively. As a serious (grade 4), late side effect, soft tissue necrosis developed in 3 cases (7%). In a univariate analysis, there was a significant correlation between lymphovascular invasion and RC (p = 0.0118) as well as cervical recurrence and DSS (p < 0.0001). Conclusion Sole postoperative HDR brachytherapy can be an effective method in case of negative prognostic factors in the treatment of early, resectable tongue tumours. Comparing the results of patients treated with postoperative BT to those who were managed with surgery or BT alone known from the literature, a slightly more favourable LC can be achieved with the combination therapy, demonstrating the potential compensating effect of BT on adverse prognostic factors, while the developing severe, grade 4 toxicity rate remains low.