Dose response of squamous cell carcinomas of the upper respiratory and digestive tracts.

Dose-response curves have been computed for 5 tumour sites of the head and neck region, using 2 regression models. In agreement with clinical observation, a significant increase has been found from moderate to high control rates with modest dose increases for exophytic tumours (T1 + T2 retromolar trigone-anterior faucial pillar and T2 + T3 supraglottic larynx). Further significant increases in local control after modest dose increases are not obtained when the control rate is already high and the slope of the dose-response curve consequently diminished. Despite unsatisfactory (50%) control rates for large heterogeneous tumours (T3 + T4 pharyngeal walls), further increases cannot be obtained without excessive doses because the curve flattens at the 50% control rate level.