Neurotoxic radiosensitizers and head and neck cancer patients--how many will benefit?

The causes for the exclusion of patients from a Phase I dose tolerance study of metronidazole as a hypoxic cell sensitizing agent in patients receiving radiation therapy for head and neck cancer have been reviewed. One hundred and fifty nine consecutive patients were assessed between October 1979 and December 1980 according to eligibility criteria decided upon prior to the study. Only 26 (23%) of 111 patients treated with radical radiation therapy entered the Phase I study. The major reasons for exclusion were a history of prior nervous system abnormality, age over 70, and refusal by some patients to participate in the study. The criteria used for patient selection for studies of hypoxic cell sensitizers (and other investigational agents) must be known so that data from each study can be assessed appropriately before being extrapolated to the general patient population. Clinical trials should be designed to take into account factors that might influence patient entry.