Dose-response analysis for nasopharyngeal carcinoma: an historical perspective.

Historical review of 118 patients with nasopharyngeal cancer treated in our institution from 1950--1978 showed a 20% improvement in tumor control for patients irradiated during the most recent period (1974--1978). This improvement was attributed to prescription of higher doses of radiation as well as improvements in technical accuracy and dose delivery to the tumor during that period. Rates of severe and mild complications were comparable and survival was not significantly altered over time despite improved tumor control. Within the range of doses delivered, there was no improvement in tumor control with increasing doses of radiation for small or large nasopharyngeal carcinomas. The dose-response analysis for tumor control was less than ideal because a number of prerequisites were lacking and because the study extended over a 28-year span during which there were significant changes in technology and physician orientation.