Completeness and accuracy of registration of colorectal cancer in Finland.

The Finnish Cancer Registry notifications of colorectal cancer diagnosed in Finland in 1975 were compared against original patient records, and hospital archives were searched for unregistered cases. 1027 cases had been registered. 4.7% of them were erroneous: 1.6% had been diagnosed before or after 1975, 1.5% had no verifiable malignancy, and in 1.7% the correct primary site was other than the colorectum. Unregistered cases amounting to 1.2% of the total were found. Only one case was unknown to the Cancer Registry, the others had been inaccurately registered as to the site of tumour or date of diagnosis. The corrected age-adjusted incidence rate (males/females) of colon cancer was 8.2/8.6 and that of rectal cancer 9.1/6.1 per 100,000. In the light of the present study, cancer registry data in Finland offer a reliable basis for timetrends and international comparisons of incidence rates of colorectal cancer.