[Population-based epidemiology of colorectal cancer: causality review].

The estimated number of new cases of colorectal cancer per year in Spain (no. 19,166) is higher than other tumour locations. 1.56 times more cases of colon cancer are registered than of the rectum, and there are 1.44 times more cases in men than in women. Incidence and mortality are lower than the average for European countries; in historical series (1973-1999) an increase can be observed by age, period and birth cohorts between 1898 and 1932. On the contrary, in the USA a reduction of mortality can be observed from 1973 to 1999 (-20.8%) and of incidence from 1985 to 1999 (-7.4%). In Spain, the average duration of the disease in years is 4.29, lower than that of the European Community (4.57), and 72% of the figure for the most favourable country (5.93). Relative survival after five years in Spain is lower than in the USA (61.9% vs. 54%). Several dietary, environmental and lifestyle factors appear to be associated with colorectal cancer, but the risk or protection of these factors are of little weight and the results of studies are at times contradictory. The reduction of incidence in the USA indicates that intervention is possible to bring about a change of trend, predictably by means of secondary prevention.