RADIOTHERAPY OF TONSILLAR AND BASE OF THE TONGUE CARCINOMA - PREDICTION OF LOCAL-CONTROL

119 patients with squamous cell carcinoma of the tonsillar region (68) and the base of the tongue (51), who received external radiotherapy w ith curative intent between 1966 and 1984, are analysed with respect t o overall treatment results, local tumour control and prognostic facto rs. Radiation doses were equivalent to 60-70 Gy in 6-7 weeks, with a m ean fraction dose of 2.4 Gy on the cobalt 60 equipment and 2 Gy on the linear accelerator. Significant differences were found between both o ropharyngeal subsites. Three-year overall survival was 57% in tonsilla r carcinoma and 38% in base of the tongue (P = 0.006); disease-specifi c survival was 70% and 47%, respectively (P = 0.005); and local contro l rates were 82% and 61% (P = 0.02). Late damage to normal tissues, li ke persistent dysphagia and osteomyelitis, were seen in 11% of patient s. Patients with large tumours in the tongue based developed significa ntly more complications (P = 0.04). T-stage and tumour subsite predict ed local control independently before start of the treatment (P = 0.02 in both cases). A significant nonlinear correlation between Normalise d Total Dose (using an alpha/beta ratio of 15 Gy) and local control ra te was found (P = 0.006), the middle range having the worst prognosis. The size of radiation field and overall treatment time did not correl ate with local control in either site. Response at the end of radiothe rapy and 6 weeks later have additional prognostic value for local cont rol, irrespective of the initial stage or subsite (P = 0.004 and <0.00 1, respectively).