Abstract A66: Disparities between African Americans and Caucasians: An analysis of the SEER Program for all anatomic sites and histological tumor types Free

Background: Studies have consistently revealed that the incidence of cancer is greater in black Americans than in white Americans for most malignant tumors. This difference has been observed primarily in cancers of the prostate gland, large intestine, breast (premenopausal), and lung. These most common cancers account for 53% of all malignant tumors in blacks and 50% in whites. However, there is no reason to assume that racial differences exist only in the most common epithelial cancers; they may also exist in other less common tumors, such as sarcomas, carcinoids, and lymphomas. Therefore, we reviewed the entire SEER Program seeking specific racial differences in patterns for the less common tumors in comparison with the more common tumors. Specifically, we investigated whether black-white differences seen in the incidence of common tumors also extend to the rare and unusual tumors and whether there are differences in the distribution of histological tumor types.

Methods: Data from NCI's SEER Program, Registry 13, (data collected from 1992 through 2005) were used to extract incident cases of tumors for blacks and whites. A total of 2,525,979 cases were reported to SEER in these years. Incident cases were stratified by tumor location, histology, age, and gender where appropriate to examine the interaction of black-white patterns of cancer incidence in the U.S. In the more commonly occurring tumors the distribution of specific histological subtypes was also compared. Incidence rates were expressed as number of cases per 100,000 persons.

Results: U.S. blacks have higher rates of a number of cancers compared to U.S. whites, including those of the oral cavity, digestive system, lung, prostate, kidney, and some uncommon tumors, such as Kaposi's sarcoma, thymomas, sarcomas, fibromas, leiomyosarcoma, and rhabdomyosarcoma. In contrast, whites have a higher incidence of cancers of the breast, ovary, testes, bladder, skin, brain, and endocrine, and hematopoietic systems, as well as childhood cancers. For some cancers, trends were increasing in whites and decreasing in blacks, and vice versa. Whites were found to have higher rates of in-situ cancers in all sites except for the GI tract.

Conclusions: Analysis of the SEER registry from 1992–2005 demonstrates differential rates of cancer incidence and histological tumor types in U.S. blacks and whites for common as well as less common occurring tumors including sarcomas. These results should be considered in any analysis of the disparities. Most conspicuous was the difference in rates for the gastrointestinal cancers and hematopoietic malignancies. Gastrointestinal system cancers were significantly more common in blacks, but cancers of the hematopoietic system were more common in whites. These differences, though unresolved, may result from genomic events or environmental, dietary, or other factors including a possible differences in carcinogenic pathways, since GI cancers usually result from point mutations, but hematopoietic cancers from translocations.