Importance of overall treatment time for the response to radiotherapy in patients with squamous cell carcinoma of the head and neck.

In the nineties, several national protocols by the Danish Head and Neck Cancer Study group DAHANCA and other randomized trials, which have included several thousand patients, were performed on squamous cell carcinoma of the head and neck, now the most common malignant disease worldwide. It is a locoregional disease and distant metastases are rarely seen at diagnosis. Radiotherapy and surgery are thus the treatment of choice, with radiotherapy being the treatment modality if organ conservation is required. Since the late eighties there has been a strong focus on the importance of overall treatment time for the outcome of curative radiotherapy for these carcinomas. Based on the results of the Danish protocols it was concluded that the schedule of radiotherapy should be given with the shortest possible overall treatment time. In fact, as a consequence of the loco-regional control rate, the disease-specific and overall survival have shown a significant dependency on the overall treatment time: when this is short, the most beneficial results are achieved. Furthermore, treatment with 6 fractions per week is now the standard radiotherapy in Denmark in most head and neck carcinomas, associated with hypoxic modification using nimorazole. The response to accelerated fractionation is however heterogeneous and until proper predictive factors can be identified and further clarified which are the patients who truly benefit from accelerated fractionation, the radiotherapy schedules should secure a sufficient dose to all patients.