Clinical assessment of tumor clearance during radiotherapy as a prognostic factor of early glottic carcinoma.

From 1967 through 1985, 358 cases of early glottic carcinoma were treated with telecobalt therapy at the Department of Radiology, Osaka University Medical School. Among 278 cases treated with 2 Gy a day, the tumor response of 262 cases at 40, 50 and 60 Gy were evaluated by direct or indirect laryngoscope. The five-year local control rates of these evaluable cases of T1 and T2 glottic carcinoma were 79% and 70%, respectively. The local control rates of T1 glottic carcinoma with tumor clearance and persistence at 40 Gy were 83% (119/143) and 64% (43/67), and those of T2 cases were 86% (18/21) and 58% (18/31), respectively. The local control rates of the cases with tumor clearance and persistence at 40 Gy were same between T1 and T2 cases. The tumor clearance rates of T1 cases were significantly higher than those of T2 cases (p < 0.005). T2 glottic carcinoma had larger tumor volumes and slower tumor regression and resulted in lower control rates compared with T1 glottic carcinoma. The difference in the radiation dose of T1 and T2 glottic carcinoma with the same clearance rate was estimated as 15 Gy using logit analysis.