Time, dose, and tumor volume relationships in irradiation of squamous cell carcinomas of the base of the tongue.

Between January 1954 and August 1971, 174 patients with squamous cell carcinoma of the base of the tongue were treated with megavoltage external beam using conventional treatment times. Since the cumulative recurrence rate was 90% by 2 years, patients surviving 2 years without primary recurrences are considered to have no evidence of disease (NED) at the primary site. The primary control rate for T1 lesions is over 90% for doses of 6000 rads in 6 weeks to 6500 rads in 6 1/2 weeks. The control rate for T2 and T3 lesions is in excess of 80% with 7500 rads in 7 1/2 weeks. The slope of a hand-drawn exclusion line for T2 and T3 lesions is 0.38. For T4 lesions no significant pattern of dose, time, and primary control could be elicited. Of the 15 mandibular necroses, only six ultimately required mandibular resection. There was a signficant relationship (p = 0.03) between the development of mandibular necroses and extension of the primary onto the mucosa covering the mandible. A plot of ret dose versus area suggested a direct relationship between the portal area (volume irradiated) and the development of mandibular necroses.