Long‐Term Results of Radiotherapy for T1a and T1bN0M0 Glottic Carcinoma

Objective/Hypothesis: The purpose of this study is to determine the prognostic factors for local control and significance of total radiation dose in T1 glottic cancer. Study Design: Retrospective study. Methods: Data from 163 patients with T1 N0 M0 Stage I glottic squamous cell carcinoma (T1a: 115, T1b: 48) who were treated with radiotherapy alone during 1976 to 2002 were analyzed retrospectively. Age, source, total dose, field size, overall treatment time, and average fraction size were set as variables in multivariate analysis. Results: The 5‐year local control rates (LCR) were 92.3% and 85.0% for patients with T1a and T1b glottic carcinoma, respectively. Only total radiation dose (P = .048) was a significant prognostic factor for local control in multivariate analysis of T1b glottic carcinoma. Local control in the higher total dose group was better than that in the lower total dose group (5 year LCRs were 100% and 76% for the group of >66 Gy and the group of ≤66 Gy, respectively. P = .024, logrank test). None of the treatment parameters were shown to be significant prognostic factors in multivariate analysis of T1a glottic carcinoma. Conclusions: Radiotherapy with a total dose of 67 to 70 Gy seemed to be required for local control in T1b glottic carcinoma. No significant benefit of total radiation dose >64 Gy was shown in the analysis of T1a glottic carcinoma.