Cancer epidemiology manuscripts often make passing reference to the fact that cancer rates are often higher among males than females, yet rarely is this theme the subject of investigation. In a hypothesis-generating exercise, we used the Surveillance, Epidemiology, and End Results (SEER) program data to compute age-adjusted (2000 US standard population) sex-specific incidence rates and male-to-female incidence rate ratios (IRR) for specific cancer sites/histologies for the period 1975-2004. The ten most frequent cancers among males were lung and bronchus (81.6 per 100,000 man-years), colon and rectum (60.2), urinary bladder (31.8), non-Hodgkin lymphoma (18.9), skin excluding basal and squamous (17.0), stomach (12.6), kidney and renal pelvis (12.4), pancreas (12.1), lymphocytic leukemia (7.8) and larynx (7.6). The respective cancers for females were breast (115.1 per 100,000 woman-years), colon and rectum (45.4), lung and bronchus (40.2), non-Hodgkin lymphoma (13.2), skin excluding basal and squamous (12.7), pancreas (9.4), thyroid (8.5), urinary bladder (8.4), kidney and renal pelvis (6.3) and stomach (5.9). The ten cancers with the largest male-to-female IRR during 1975-2004 were Kaposi sarcoma (32.00), lip (7.24), larynx (5.14), mesothelioma (4.64), hypopharynx (4.10), urinary bladder (3.78), esophagus (3.49), tonsil (3.05), oropharynx (2.93), and other oral cavity and pharynx (2.72). Only five cancer sites had a higher incidence in females compared to males: breast (0.01), peritoneum, omentum and mesentery (0.29), thyroid (0.37), gallbladder (0.56), and anus, anal canal and anorectum (0.77). Of the 47 cancers analyzed, 19 had a male-to-female IRR higher than 2. The largest, consistent increases in male-to-female IRR during 1975-2004 were for cancers of the tonsil, oropharynx and esophagus. Cancers for which the male-to-female IRR has been decreasing include: pancreas, gum and other mouth, retroperitoneum, larynx, ureter, lip, nose, nasal cavity and middle ear, Hodgkin lymphoma, cranial nerves and other nervous system, peritoneum, omentum and mesentery, kidney and renal pelvis, thyroid, and lung and bronchus. Male-to-female IRRs may be informative because they are likely not to be subject to artifactual trends attributable to changes in diagnostics, prevention, tumor definitions and coding practices. In addition, male-to-female IRRs may be indicative of differential exposures and/or responses important in the pathogenesis of cancer. Higher levels of tobacco use and alcohol consumption among males have likely contributed to many of the elevated IRRs, but other exposures have also certainly played a role. These observations should serve as a foundation for further studies of sex differences in cancer etiopathogenesis.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):B12.

Seventh AACR International Conference on Frontiers in Cancer Prevention Research-- Nov 16-19, 2008; Washington, DC