Is toxicity really necessary? I. The question

A general concept in cancer chemotherapy is that host toxicity is necessary to effect a positive tumor response. An analysis of the relationship between host toxicity and tumor response was made utilizing data from 956 patients receiving 5-FU, mitomycin C, AB-132, chlorambucil or 6-MP. Several criteria were used to categorize host toxicity in testing its relationship to the incidence of objective tumor response based on a 50% reduction in tumor size. The proportion of responses was not observed to be higher among patients exhibiting signs of toxicity than among those free of such toxicity. The results suggest that there may not be as close a relationship between host toxicity and tumor response as generally believed. More specific studies are needed before the title question can be answered definitely.