Accelerated versus conventional fractionation in the postoperative irradiation of locally advanced head and neck cancer: influence of tumour proliferation.

Fifty-six patients with locally advanced head and neck squamous cell carcinoma were subjected to adjuvant radiotherapy after radical surgery with randomisation to either conventional fractionation (CF), comprising 50 Gy/25 F/5 weeks, or to accelerated hyperfractionation (AHF) to a dose of 42 Gy/30 F/11 days (3 F/day), a dose/F of 1.4 Gy and an interfraction interval of 4 h. The in vitro [3H]thymidine labelling index (TLI) was determined as an indicator of tumour proliferation. Early mucosal reactions were somewhat more severe after AHF than after CF and the peak was attained earlier. The actuarial 3-year complication rate was significantly lower in the AHF (64%) than in the CF group (87%). This is probably related to a smaller fraction size and a lower total dose. The overall 3-year disease-free survival amounted to 46 +/- 7%. Sex, the anatomical site, the nodal status, the performance status and TLI have been shown to be significant prognostic factors, but only the latter two proved to be independent covariates. Overall, the type of fractionation did not seem to influence survival. However, AHF seemed to offer higher survival probabilities in fast growing tumours and this attained a significant level for tumours with TLI > 10.4% (Tpot < 4.5 days). However, CF and AHF were associated with similar survival rates in slowly growing tumours. The relative effectiveness of the CF and AHF schedules is predictable on the basis of the linear-quadratic system. In the case of tumour response, a time factor has to be included assuming that accelerated repopulation of microscopic residues occurs from the outset.(ABSTRACT TRUNCATED AT 250 WORDS)