A marked increase in the incidence of colorectal cancer over two decades in southwest Finland.

The Finnish Cancer Registry's data on all colorectal cancer cases from 1971 to 1990 in southwest Finland, an area of mean population of 433,000, were analyzed. The age-adjusted incidence of colon cancer per 100,000 population increased in men from 8.5 in 1971-1980 to 13.5 in 1981-1990 and in women from 10.3 to 13.1. The incidence of male rectal cancer increased from 9.8 to 11.1 and in women from 6.4 to 7.1. The proportion of elderly patients clearly rose and, in 1981-1990, patients over 65 years of age had 68.4% of all colon cancers and 73.9% of all rectal cancers. There was a proximal shift in the site distribution of cancers: the proportion of rectal cancers decreased from 45.9% in 1971-1980 to 40.9% in 1981-1990. This change was most marked in men. There was no change in the spread and operability of colorectal cancers during the two decades. There was an increase in colon cancer mortality while the mortality of rectal cancer cancer slightly decreased.