Multivariate analysis of cancer mortalities for selected sites in 24 countries

In order to analyze the pattern in the geographical distribution of cancer death in 24 countries of the world, correlation coefficients were calculated between pairs of mortality rates of different cancer sites, using the data for 13 sites in males and 14 sites in females over 18 years from 1950 to 1967. Then factor analysis by means of varimax method was performed on 13 x 13 correlation matrix for males, 14 x 14 correlation matrix for females and 27 x 27 correlation matrix for males and females combined. As a result of factor analysis, three factors are extracted, which are commonly recognized in both males and females. The first factor has high positive factor loadings on pancreas, prostate (for males), skin, and intestine cancers, and negative loadings on stomach and liver cancers. The second factor has high positive factor loading on rectum, intestine, and lung cancers, and the third factor on larynx, oral, and esophagus cancers. Factor analysis based on 27 x 27 correlation matrix revealed that the third factor of both sexes are heterogeneous with regards to the distributions of the factor score. In order that we may find some clues to develop an etiological hypothesis for each site of cancer, we obtained the correlation coefficient between the scores of the extracted factors and the variables on food and environmental agent, and performed stepwise regression methods as well. One of the most striking results we obtained was that excessive drinking of alcohol and the lack of appropriate intake of fruit are suspected as etiological promoters in the pathogenesis of oral, esophagus, and larynx cancers in males.