The Ongoing Search for the Sources of the Breast Cancer Survival Disparity

Abstract

In the search for explanations for the persistent disparity in outcomes after breast cancer diagnosis between African American and white American women, there has always been something of a divide in the research community. Social and economic differences between the groups are too glaring to ignore, and have significant health consequences across a spectrum of diseases, including cancer. On the other hand, in a disease as heterogeneous as breast cancer, biology is destiny, in ways that we sometimes understand and in others that remain elusive. Thus, when tumor characteristics associated with poor prognosis are noted in greater frequency among black women, an obvious explanation for the disparity is presented. Researchers overly favoring either socioeconomic or biologic explanatory pathways do so at some peril, and consensus has built around the conclusion that both of these factors, and others, must be considered concurrently. However, it has proven difficult to adequately account for the complex constellation of factors that contribute to cancer disparities in any one study.The report by Newman et al in this issue of the Journal of Clinical Oncology attempts to bring the role of socioeconomic status (SES) to the forefront by synthesizing results from studies of black/white disparities that either included socioeconomic measures or were conducted in "equal-access" health care situations. 1 The investigation is an update of an earlier investigation that includes additional studies published since 2001. 2 The primary conclusion, that accounting for SES measures does not completely explain disparities, seems to be supported by many of the individual studies, as well as the combined estimate from the metaanalysis. Some reservations may be in order, however, based on the methodologic challenges and data limitations inherent in the individual studies summarized. Also, whether biologic explanations therefore gain more credence based on these findings is an inference that must be considered with some caution.Meta-analysis is a valuable research tool, as it forces critical evaluation of the published literature and a quantitative summary that hopes to move beyond seemingly informed opinion. However, even in the case of randomized trials, individual study idiosyncrasies are such that the whole may be less than the sum of its parts, and the state of the art has moved to analysis of patient-level data to avoid some of these difficulties. In the case of disparate types of studies over a broad time span and reliance only on summary effect measures, the analytic task and the interpretation of the results are even more challenging. The authors do apply the appropriate methodology to obtain their summary estimate, which one can either take at face value, or if preferred, choose to examine and weigh the individual studies less formally (Figure 1 of Newman et al). 1 Roughly half of the studies show a relative mortality excess below the summary estimate of 27%, and half find a greater excess. Interestingly, another meta-analysis by...

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