Disparities in breast cancer incidence across racial/ethnic strata and socioeconomic status: A systematic review

Objectives: A higher incidence of breast cancer has been reported both in white women and women of higher socioeconomic status (SES) compared to women of other races and lower SES, respectively. We explored whether differences in SES can account for disparities in breast cancer incidence between races, Methods: We identified several studies published between 1990 and 2007 that addressed disparities in breast cancer incidence across racial and socioeconomic strata. For each study, we calculated incidence rate ratios (IRRs) for breast cancer incidence in the highest strata to lowest strata of SES for white, black, Hispanic and Asian/Facific-Islander populations. We then used these IRRs to compare trends in SES and breast cancer incidence between races and across studies. Results: The studies we identified revealed that the magnitude of the disparity in breast cancer incidence between races decreases with increasing SES. While individual census-tract based studies' methods of assessing the association between SES and breast cancer incidence did not identify consistent trends between races, adjustment for risk factors closely correlated with SES eliminated the statistical differences in breast cancer incidence between women of white, Hispanic and Asian/Pacific-Islander, but not black, ethnicity. Conclusion: We found that racial differences in breast cancer incidence can largely be accounted for by ethnic differences in SES among white, Hispanic and Asian/Pacific-Islander women, but not between these populations and black women. We further highlight important differences in methodology between previously published studies that may account for their disparate findings.