Postoperative brachytherapy in epidermoid carcinomas of the floor of mouth

Purpose : To analyse the interest of postoperative brachytherapy (BT) in a group of patients with a high risk of local relapse (positive or close surgical margins) for squamous cell carcinoma of the floor of mouth (SCCFM). A comparison with postoperative external beam irradiation in a group of patients of medium risk of local relapse (EBI) for SCCFM with free margins is performed to estimate the benefit of BT. Material et methods : From 1979 to 1992, a first group of 32 patients with a SCCFM (12 T1-2, 20 T3-4-X) received an Ir 192 low dose rate BT using plastic tubes (+EBI for 20 patients) after surgery with positive or close margins. BT was performed in 1 or 2 plans along the surgical scar. When the tongue or the remaining floor where sutured to the internal face of the inferior lip or of the buccal mucosa, a 'bridge technique' was used. The mean dose of BT was 57 Gy (range : 50 - 60) for exclusive BT and 22 Gy (range 15 - 30) when used as a boost (mean EBI dose 50 Gy). During the same time a second group of 36 patients (12 T1-2, 24 T3 - 4 - X) with SCCFM with free surgical margins received a exclusive postoperative EBI (mean dose in the surgical scar was 50 Gy). Excluding the postoperative margin, these 2 groups were comparable for other prognostic factors (tumoral size, node status, age, sex and type of surgery). Results : The mean follow up was 46 months (range : 5 - 145). For BT and EBI groups, the 5-year results (Kaplan-Meier) were respectively : overall survival 62% and 43%, specific survival 74% and 53%, local control 81% and 60% (p = 0.09) (Log Rank) and severe complications (4(32)) and (1(36)). Conclusion : Postoperative BT achieves a good local control for patients with close or positive margins by increasing the dose to the surgical scar with a good tolerance. Given these good results, we confirm this indication for these patients