Impact of Sociodemographic Factors, Hormone Receptor Status, and Tumor Grade on Ethnic Differences in Tumor Stage and Size for Breast Cancer in US Women

The importance of sociodemographic factors and tumor biomarkers in explaining ethnic differences in tumor stage and size at diagnosis was investigated in over 106,000 female breast cancer patients reported during 1992-1996 from 11 US population-based cancer registries. Japanese and non-Hispanic White women tended to be diagnosed at an earlier stage, with smaller diameter tumors and with a lower tumor grade than women from seven other ethnic groups. Statistical adjustment for individual- and group-level sociodemographic factors produced 50-80% reductions in the odds ratios for distant (vs. localized) stage and larger (vs. <1 cm) tumor size among Black women and Hispanic women. These factors also helped to account for tumor stage and size variation among most other ethnic groups. Consideration of hormone receptor status and tumor grade had little effect on the ethnic patterns. Although small, elevated odds ratios remained for some groups, our results suggest that sociodemographic factors accounted for many of the observed ethnic differences in breast cancer stage and tumor size at the time of diagnosis. Because most of the sociodemographic variables were aggregate measures, it is possible that residual confounding by socioeconomic position could explain the persistence of slightly elevated odds ratios in some ethnic groups.