Definitive Radiation Therapy for Early Glottic Cancer: Experience of Two Fractionation Schedules

OBJECTIVES: The authors would report the results of definitive radiation therapy (RT) for early glottic cancer by two different radiation dose schedules. METHODS: From February of 1995 till June of 2008, 157 patients with T1-2N0 glottic cancer were treated with curative RT at Samsung Medical Center. All patients had squamous cell carcinoma, and there were 89 patients (56.7%) with T1a, 36 (22.9%) with T1b, and 32 (20.4%) with T2. Two different radiation dose schedules were used: 70 Gy in 35 fractions to 64 patients (40.8%, group A); and 67.5 Gy in 30 fractions to 93 patients (59.2%, group B). The median treatment durations were 50 days (range, 44 to 59 days) and 44 days (range, 40 to 67 days) in the groups A and B, respectively. RESULTS: The median follow-up durations were 85 and 45 months for the groups A and B. No severe late complication of RTOG grade 3 or higher was observed, and there was no difference in acute or chronic complication between the groups. Twenty-four patients experienced treatment failure: local recurrence only in 19 patients; regional recurrence only in one; combined local and regional recurrence in four; and systemic metastasis in none. The overall 5-year disease-free survival and disease-specific survival rates were 84.7% and 94.8%. The disease-free survival rate in the group B was better (78.3% vs. 90.8%, P=0.031). This difference was significant only in T1 stage (83.4% vs. 94.6%, P=0.025), but not in T2 (62.7% vs. 60.6%, P=0.965). Univariate analysis showed that the tumor extent, cord mobility, T-stage, and the dose schedule had significant influence on the disease-free survival, and multivariate analysis showed that only the tumor extent and the dose schedule were associated with the disease-free survival. CONCLUSION: Superior disease-free survival could be achieved by 2.25 Gy per fraction without increased toxicity over shorter RT duration, when compared with 2.0 Gy per fraction.