Time, dose and volume factors in interstitial brachytherapy combined with external irradiation for oral tongue carcinoma

This is a retrospective analysis of 136 patients with squamous cell carcinoma of stages I and II of the oral tongue who were treated with interstitial brachytherapy alone or in combination with external irradiation between 1976 and 1991. Control of the primary lesion and the occurrence of late complications were analyzed with respect to dose, time and tumor size with the Cox hazard model. The 5-year survival rates for stages I and II were 84.5% and 75.6%. The 5-year primary control rate was 91.3% for stage I and 77.3% for stage II (p<0.05). Local control and survival rates were comparable with those of other modalities. The significant factor in local control was stage. For lesions more than 30 mm in diameter, local control was rather poor in the group given only brachytherapy compared with the group given combined therapy. After 30 Gy of external irradiation, local control was better at a brachytherapy dose >50 Gy compared with a brachytherapy dose <=50 Gy. Mucosal ulcer occurred frequently with increasing total dose and tumor volume. Bone necrosis increased significantly with increasing external irradiation dose. We suggest that external irradiation of 30 Gy followed by brachytherapy of 52 Gy is a better choice for T2 lesions >30 mm. Late complications should be reduced by using a spacer, improvements in dental and oral hygiene, and a sophisticated implant method. (author)