Economic evaluation of trends in cancer therapy. Marginal or average costs?

Evaluating the use of resources as well as outcomes in cancer therapy is increasingly becoming recognized by both clinicians and others as a legitimate and indeed even desirable activity. While this trend is to be welcomed if it facilitates the efficient use of resources for cancer care, there are dangers in applying estimates of unit costs, in particular average costs to the evaluation of trends in practice in cancer therapies. This article examines the use of appropriate measures of average and marginal cost in the economic evaluation of developments in cancer therapy, taking illustrations from radiotherapy and chemotherapy.