Correlation of incidence rates for selected cancers in 29 census sub-divisions of Alberta, Canada, 1961-1981

Age-adjusted incidence rates for males and females for 36 cancer sites across 29 census sub-divisions of the province of Alberta were correlated with one another. It was hypothesized that cancers which vary together across geographical areas may have common aetiological factors. The correlations were measured by the Pearson product moment coefficient, r, and illustrated by scatter graphs and regression lines. For males moderate correlations were found between prostate and skin cancer and between prostate cancer and non-Hodgkin's lymphoma. Also moderately correlated were male stomach and small intestine cancers and cancers of the bladder and the buccal cavity and pharynx. Specific site correlations for cancers in females were generally higher than for cancers in males. The highest correlations were found between cancer of cervix (invasive) and cancer of trachea, bronchus and lung, between multiple myeloma and cancer of brain and nervous system, between acute lymphatic leukemia and cancer of the bone and connective tissue, and between melanoma and cancer of bone and connective tissue. Although all these correlations are moderate they nevertheless indicate substantial relationships. Possible common aetiologic factors for correlating pairs of cancers are discussed.