The effect of overall treatment time of radiation therapy on local control of T1-stage squamous cell carcinoma of the glottis.

From 1975 to 1990, 72 patients with T1 glottic cancer, excluding a verrucous type of carcinoma, were treated with radiation therapy (RT). All treatments were given with a standard fractionation of 2 Gy per day. The total dose to the tumor ranged from 60 to 70 Gy. Six patients received a split-course RT. The overall local control rate was 87% at 5 years. Forty-one patients who completed RT in 45 days or less had a 5-year local control rate of 95%. Sixteen patients who completed a treatment course in 46 to 49 days had a local control rate of 81%. Fifteen patients with a treatment course of more than 50 days had a local control rate of 73%. There was a statistically significant difference in local control rates among the three groups (P<.05). The split-course RT group had a 5-year local control rate of 50%; that rate was statistically significantly inferior to that of the continuous course group (P<.001). Multivariate analysis also showed that an interruption of the treatment course was an important parameter in relation to the local control. The prolongation of standard RT schedules adversely affected local control of T1 glottic carcinoma and, therefore, should be avoided whenever possible.