From hazard identification to weighing the benefits and drawbacks of prevention.

In this commentary, we briefly summarize and give examples of evaluations done by the International Agency for Research on Cancer, WHO (IARC-WHO, Lyon, France) about the identification of carcinogenic substances or agents and the evaluation of the efficacy and effectiveness of cancer preventive substances, agents or strategies. In the 1970’s the IARC initiated a series of Monographs on the Evaluation of Carcinogenic Risks to Humans for the purposes of primary prevention. During the last 35 years of the IARC Monographs, many agents that are important to the public health perspective have been evaluated. The agent or exposure is described and classified according to the wording of one of the following groups: group 1, carcinogenic to humans; group 2A, probably carcinogenic to humans; group 2B, possibly carcinogenic to humans; group 3, not classifiable as to its carcinogenicity to humans; group 4, probably not carcinogenic to humans. In 1997, the IARC started a new series of handbooks, the IARC Handbooks of Cancer Prevention, which aimed for the evaluation of efficacy and effectiveness of cancer preventive agents and strategies. The process of evaluation is quite similar to the IARC Monographs. In total, 10 Handbooks were published in topics such as mammography screening, cervical cancer screening, consumption of fruits and vegetables, cruciferous vegetables, and weight control and physical activity. We discuss in general terms ways of preventing cancer and of evaluating preventive strategies, giving as example mammography screening.