Gender-related differences in the distribution of thoracic versus abdominal malignant mesothelioma

The relationship between malignant mesothelioma (MM) and asbestos is well established, but the determinants of host factor susceptibility of MM are not. This study probes susceptibility issues by examining gender-related differences in the distribution of 417 thoracic and 42 abdominal cases of MM from 1988-1989 California Cancer Registry databases. The age-adjusted incidence rate ratio (IRR) for male/female thoracic MM was 6.9 (95% confidence interval [CI]; 5.0-9.6) consistent with greater occupational exposure among men. However, the IRR for male/female abdominal MM was 1.5 (95% CI: 0.6-3.6). Also, average age of onset for thoracic MM was greater than for abdominal MM. Thus, some abdominal MMs may be due to nonoccupational asbestos exposure, occurring over a lifetime, interacting with host factor susceptibility. This study gives impetus to research regarding the importance of host factors and nonoccupational asbestos exposure in the etiology of malignant mesothelioma.