Correlations between cancer incidence rates from the Canadian National Cancer Incidence Reporting System, 1969-78.

Incidence rates for 19 cancers in females and 16 cancers in males have been computed from data reported by 8 Canadian provinces to the National Cancer Incidence Reporting System between 1969 and 1978. The rates, very similar in absolute and relative magnitude to those reported by the U.S. Third National Cancer Survey, have been used to examine patterns of correlation between various cancers within the 8 provinces. There is strong evidence of positive associations between a number of cancers, including a number of associations that have been reported in other similar correlational studies. Correlations that may be of particular interest in suggesting etiologic factors in common include clusters of smoking-related cancers (buccal cavity with pharynx, larynx, lung, and bladder), female sexual cancers (breast, corpus uteri, and ovary), and a group of cancers that have shown correlation in other studies (i.e., cancers of the pancreas and kidney, leukemias, lymphomas, and cancer of the prostate gland). Organs in the gastrointestinal tract (esophagus, stomach, colon, and rectum) anatomically close to each other show a high positive correlation in both females and males, but the further apart the organs are the lower is the correlation; these observations are consistent with other evidence of varying dietary etiologies. Two individual correlations of particular interest are those between female brain tumors and female bladder cancer (two cancers for which little is known of the etiology for a large percentage of them) and those between female breast cancer and female lung cancer. This study, the largest correlational study of incidence data reported to date, demonstrates the utility of such simple correlational analyses.