During 1981-1988 63 patients with squamous cell carcinoma of the oral tongue (27 females and 36 males) were treated with radical surgery and postoperative split-course radiotherapy. The 3-week rest period was compensated with a 10% increase in the total radiation dose to 66 Gy. The local control rate was 76% in stage I, 71% in stage II, 45% in stage III and 0% in stage IV. Failures were observed in 25 (40%) patients, and 8 patients died of intercurrent diseases. For further analysis the material was stratified in three groups according to the time interval between surgery and postoperative radiotherapy: < 6 weeks, 6-8 weeks and > 8 weeks. The local control rate in the three strata were 75, 57 and 44%, and the 5-year actuarial survival 61, 46 and 30%, respectively. In the logistic regression analysis and the proportional hazard's regression analysis the histologic grade of the primary tumour and the time interval between surgery and the start of radiotherapy were the most important factors influencing respectively local control and time to recurrence. However, it appeared that the lengthening of the time interval was often caused by factors or events which directly can influence the prognosis, such as surgical complications, infections and poor general condition. When cases with such special causes for lengthening of the interval were excluded, the effect of the time interval nearly completely disappeared. It would seem that a final evaluation of the effect of the time interval requires a prospective randomized trial. The same may well hold true for reliable evaluation of the influence of overall treatment time.
