Underrepresentation of minorities and poor women in studies of gene-expression profiling of breast tumors potentially increases disparities in breast cancer outcomes

Background: New prognostic tests, such as gene-expression profiling (GEP) of breast tumors, are purported to prolong survival and improve the quality of life for many breast cancer patients. Biological and social factors affect breast cancer incidence, progression, and mortality in diverse U.S. populations. Methods: We drew on the CDC's Evaluation of Genomic Applications in Practice and Prevention Program Working Group report, “Impact of GEP tests on breast cancer outcomes” aug¬mented by more recent literature to examine evidence on testing and validation in minority populations of three GEP assays that are used in the USA to predict clinical outcomes in patients with breast cancer. Results: Of the 22 studies we examined, six, reported race/ethnicity. Of over 6500 total study participants, about 7% as nonwhite and 2% as black. Of the six studies that reported race/ethnic¬ity, approximately 23% of patients were nonwhite, 6% was black. Outcomes were not separately evaluated by race or, generally, by estrogen receptor status. No studies reported subjects' socioeconomic status (SES).Conclusions: Evidence-based medicine has the potential for greatly improving popula¬tion health. However, under-representation and under-reporting of minority racial/ethnic groups, and the lack of information about SES in GEP studies limits the evidence-base for evaluating the utility of the tests in diverse populations. The black-white breast cancer mor¬tality gap could persist or even widen if such tests are not developed for, validated in, and accessed by underserved and minority populations. We need to build a large and diverse evidence base for GEP and other emerging technologies in personalized medicine.