To answer patients, caregivers and professionals needs, the "Plan Cancer" has been presented by the French President on the 24 March 2003. This plan's measures form the concrete elements of a modern health care policy against cancer. It's likely that a plan cancer succeeding to improve patients' survival and quality of life would not be associated with a decrease in health care expenses. However, the plan cancer should target to improve our health care system productivity, i.e. to ensure that the gain in years of life (and in welfare) for each Euro invested would increase. To reach this objective, the plan cancer should consider four problems that health economics may highlight. The impact of biomedical innovations in terms of returns; the question about the rational threshold for allocating resources; the influence of the heterogeneity of the medical practice; the role of patients' preferences. We expect that emphasising these difficulties would allow for health economics to be better considered in the research against cancer and to be clearly distinguished from opinion surveys. It's the best way for social surveys based on direct interview of representative samples of patients' and their relatives to give a useful tool for democratic reflection.