Racial and ethnic variations in uterine corpus cancer incidence, United States, 2001-2003

A88

Objective: Previous studies of uterine corpus cancer have largely focused on differences between white and black women with endometrial cancer. We examined racial and ethnic variations in uterine corpus cancer incidence in the US, including racial and ethnic groups previously less studied, and non-endometrial uterine corpus cancers.
 Methods: Data are from the 2001-2003 National Program of Cancer Registries and the Surveillance, Epidemiology and End Results Program. Data are from state cancer registries meeting quality criteria for all years and cover 90.3% of the U.S. population. We included females with a microscopically confirmed diagnosis of invasive uterine corpus cancer (n=97,098). We grouped individual cancer histologies into 3 major histologic groups (epithelial tumors and related lesions, mesenchymal tumors, mixed tumors). We calculated incidence rates (per 100,000) age standardized to the 2000 US Standard Population by age group and tumor characteristics for the 3 major groups. Within major histologic groups, we stratified by race and ethnicity. Because of the large number of cases and comparisons, we considered differences with p<.0003 compared with whites (for race) or non-Hispanics (for ethnicity) to be significant.
 Results: Asian/Pacific Islander (API) women had lower rates of epithelial cancers than white women (12.8 vs. 21.7, p<.0001). Within epithelial cancers, APIs had the second highest rate of endometrioid adenocarcinoma (AC) (8.4), and a lower rate of serous AC (0.5 vs. 0.9, p<.0001). Rates of mesenchymal and mixed cancers among APIs and whites were similar. Hispanics had lower rates than non-Hispanics of epithelial cancers (16.0 vs. 21.3, p<.0001) and similar rates of mesenchymal and mixed cancers. Rates for most individual histologies did not differ by ethnicity, although Hispanics had lower rates of endometrioid AC (9.2 vs. 13.2, p<.0001). American Indian/Alaska Native (AIAN) women had lower rates of epithelial cancers than white (11.5 vs. 21.7, p<.0001) or black women (14.9). White women had the highest rates of epithelial cancers, although black women had the highest rates of mesenchymal (0.9 vs. 0.6 for whites, p<.0001) and mixed cancers (2.0 vs. 0.9, p<.0001). For individual histologies, black women had higher rates than white women of serous AC (2.0 vs. 0.9, p<.0001), clear cell AC (0.5 vs. 0.3, p<.0001), carcinosarcoma (1.9 vs. 0.8, p<.0001) and leiomyosarcoma (0.6 vs. 0.3, p<.0001). Black women also had lower rates of low grade (3.9 vs. 9.3, p<.0001 for grade I; 3.9 vs. 6.7, p<.0001 for grade II) and localized stage epithelial cancers (8.5 vs. 16.0, p<.0001); and had higher rates of high grade (4.5 vs. 3.6, p<.0001 for grade III; 0.6 vs. 0.5, p=.0001 for grade IV) and distant stage disease (1.6 vs. 1.1, p<.0001).
 Conclusion: In a dataset with >90% U.S. population coverage, uterine corpus cancer rates were generally similar or lower among API and AIAN women than among white or black women, and among Hispanic vs. non-Hispanic women. Black women had higher rates of cancers previously suggested to have worse prognosis, including serous AC, clear cell AC and carcinosarcoma. Further research is needed to help explain and address differences in incidence among racial and ethnic groups. Findings will help planners understand burdens among groups, and provide a baseline for future surveillance of epithelial, mesenchymal and mixed cancer rates for these groups.