[Cancer prevention and screening].

We show that cancer mortality is decreasing with time for most sites of cancer, the most notable exception being lung cancer in women. Cancer incidence is a misleading indicator because it can depend on diagnostic procedures, as observed with prostate cancer in men and breast or thyroid cancer in women. Overall these data contradict the alarming information that cancer is on the increase, which is widespread by the media and some health professionals. To be efficient in the prevention of cancer one needs to identify its causes and measure their relative importance. The major causes of cancer in France today are tobacco and alcohol. The variations of the price of tobacco and their effects on sales show the importance of the taxation policy. Cancer screening is practised in a way defying logic : a screening procedure with a demonstrated high efficacy is not part of a national programme whereas a useless and even potentially harmful procedure is very widely used.