Colorectal cancer.

International trends in the incidence, mortality and survival for colorectal cancers are heterogeneous, probably because of interpopulation diversity in trends in risk factors and in systems of medical care and screening programmes. Broadly, colorectal cancer rates correlate with the adoption of a western lifestyle, and, depending on each country's stage of transition, colorectal cancer incidence can be increasing (often rapidly), levelling or declining. In high risk countries, although decreases in incidence might be expected in the longer term in response to current dietary trends, some short term increases in incidence may result from the promotion of screening activities. The growing proportion of early stage tumours detected in screened populations will eventually be reflected in lower mortality rates.