T1 and T2 squamous cell carcinomas of the floor of the mouth: Results of brachytherapy mainly using 198Au grains

Purpose : To investigate the effectiveness of brachytherapy provided by this institution over a 25-year period, and to specifically verify the efficacy of 198 Au grain therapy, this study evaluated the outcomes in patients given brachytherapy for T1 and T2 squamous cell carcinomas (SCCs) of the floor of the mouth. Methods and Materials : A retrospective analysis of data from 90 patients with T1 and T2 SCCs of the floor of the mouth who underwent brachytherapy between 1965 and 1989. Therapy mainly consisted of 198 Au grain implants with or without external irradiation. As for the brachytherapeutic source, 15 patients were treated with radon seeds, 60 with 198 Au grains, 10 with radium needles, 3 with cobalt needles, and 2 with iridium hairpins. Based on the 1987 International Union Against Cancer (UICC) classification, the SCC stagings and number of cases per staging follow : Stage I (T1N0), 21 cases ; Stage II (T2N0), 55 cases ; and Stage III-IV (T1-2N1-2), 14 cases. The minimum follow-up time was 3 years. Results : The local control rates of these SCCs, based on tumor size, were 89% for T1 lesions, 76% for T2a (≤ 3 cm) lesions, and 56% for T2b (> 3 cm) lesions, and 82% for T1-2 lesions without a gingival involvement, in contrast to 55% for lesions with a gingival involvement (p < 0.05). The 5-year, cause-specific survival rates by staging were 95% for T1N0, 79% for T2N0, and 54% for T1-2N1-2. For patients given 198 Au grain brachytherapy, local control was achieved in 93% of the T1 lesions, 79% of the T2a lesions, and in 56% of the T2b lesions. Further, the incidence of severe complications requiring surgery was low (5%). Conclusion : For T1N0 and T2aN0 SCCs of the floor of the mouth, excluding lesions with a gingival involvement, 198 Au grain brachytherapy alone or in combination with external radiotherapy was found to be efficacious.