Multiple fractions daily for head and neck cancer: spinal cord effects and other late results.

Reports of late spinal cord damage after multiple fractions daily radiotherapy regimens for head and neck cancer are infrequent, but increasing. We have reviewed our experience of head and neck cancers treated thrice daily to examine this problem. Between 1982 and 1990, 65 patients with advanced head and neck cancer were treated by primary radiotherapy using three small fractions delivered on 5 days per week, with an inter-fraction interval of 3-4 hours during normal working hours. In 25 patients, the cervical spinal cord received > 39 Gy. In 13 patients, 39.6 Gy was given in 1.1 Gy fractions, and five received 41.8 Gy in 1.1 Gy fractions, two received 45.1 Gy in 1.1 Gy fractions and five received 45 Gy in 1.5 Gy fractions. Eleven of these patients have survived over 2 years, and can be assessed for late spinal cord damage. Ten of these received 1.1 Gy fractions with no cord damage. The only 2-year survivor whose cord received 45 Gy in 1.5 Gy fractions has developed mild, non-progressive long tract signs. Other late side effects were equivalent to those after conventionally fractionated radiotherapy. Tumour control was good, especially for the larynx. We feel that, for radiotherapy given with three small fractions daily and an inter-fraction interval of 3-4 hours, the spinal dose should not exceed 40 Gy.