Do cross-registry comparisons of Black and White Americans provide support for N-acetylation as an important determinant for urinary bladder and other tobacco-related cancers?

Tobacco smoking is an unequivocal risk factor for cancers of the larynx, lung, pancreas and urinary bladder. Whereas African-Americans demonstrate higher laryngeal, lung and pancreatic cancer rates than their Caucasian-American counterparts, they paradoxically have only approximately half of the urinary bladder incidences. One possible explanation is their N-acetyltransferase (NAT) status, since this enzyme is responsible for metabolism of arylamines in smoke and blacks are reported to have a higher rate for rapid acetylation than whites. However, other tobacco-related cancers are also linked to slow acetylation so that African-Americans might therefore also be expected to have lower incidences of other tobacco-related cancers. The present investigation was conducted with data from Cancer Incidence in Five Continents Vol VIII to assess whether there might be correlations between incidence rates for four major cancers across registries in the United States. Cluster analysis demonstrated clear separation of the white and black populations for all states, and significant correlations were observed between bladder and laryngeal cancers, and also for lung and laryngeal cancers, for both Blacks and Whites. Striking similarities in the plots for urinary bladder incidence against all three of the other cancers suggests the existence of a factor specific to the bladder. A review of black-white ratios for cancer incidences in all major body sites in both sexes and the published literature for NAT polymorphisms provided evidence that this might indeed be arylamine exposure, although other factors could also be involved.