Abstract

Chemoprevention, a clinical analogue of public-health prevention strategies, is often proposed as a method of reducing cancer incidence and mortality but has a wider context in possibly lowering risk of other chronic diseases. Chemoprevention has had some successes but a number of highly visible failures; failures, in this context, encompass not only null results but, more crucially, a finding of harm when the agent was specifically hypothesized to protect or reduce risk. Even if the agents and endpoints are diverse and the nature of the outcomes is different, are there some common elements that may explain such failures? Are there biologic processes that act to buffer the effectiveness of chemopreventive agents? What light does our experience with chemotherapy shed on the theory and practice of chemoprevention? Do we even have a theory that underpins chemoprevention? Do we need to reconsider the whole enterprise? .