Results of a phase I study to determine the maximum tolerated dose of capecitabine when given concurrently with radical radiotherapy in the treatment of squamous cell carcinoma of the head and neck.

Capecitabine is preferentially converted to 5-fluorouracil within tumours, exploiting the higher levels of thymidine phosphorylase (TP) found in areas of poor perfusion and hypoxia. In addition radiation leads to up regulation of TP expression. To exploit these advantages of capecitabine as a synchronous chemoradiotherapy agent patients with advanced squamous cell carcinoma of the head and neck were recruited into a phase I non-randomised dose finding study. Capecitabine was given twice daily, 7 days a week at a dose starting at 350 mg/m(2) bid. Radiotherapy using a beam directed technique was prescribed to 55 Gy in 20 fractions over 4 weeks. A total of 24 patients were treated. Dose-limiting toxicity (grade IV mucositis) was reached at a capecitabine dose of 550 mg/m(2) bid. Radiotherapy was completed without delay in all cases. There was no systemic drug related toxicity. Capecitabine offers the prospect of an orally administered drug for use synchronously with radiotherapy, which in doses up to 500 mg/m(2) bid is well tolerated.