Correlations between cancer mortality rates from various Italian regions.

Death certification rates from 17 non-sexual and 4 sexual cancers were used to examine patterns of correlation between various cancers within the 20 Italian regions. A large number of strongly positive correlations emerged, reflecting the geographical distribution of cancer mortality in Italy which shows substantially higher rates for several common sites in northern areas. The most notable findings were the high positive correlations between various tobacco-related cancers in both sexes (however somewhat higher in males), the positive correlations between most intestinal sites and between a well defined group of other cancers including intestines in both sexes, breast and ovary in females and prostate in males, previously described in several widely heterogeneous populations. Various alcohol-related cancers showed high positive coefficients in males but not in females. Several suggestions which emerged from previous correlation studies but which generally lacked convincing biological or epidemiological consistency were not confirmed by the present data. Conversely, a few strong correlations emerged in the present study which are not explainable in terms of available knowledge of the causes of cancer, or obvious confounding. Though probably incidental, the existence of these correlations between cancers with widely heterogeneous or largely undefined etiology is still an indirect indication that these neoplasms are largely avoidable, since it is unlikely that the same genetic determinants are strongly associated with such different malignancies.