Disparities in Breast Cancer Outcomes: Receipt of Chemotherapy Is Only Part of the Story

Ethnic disparities have been demonstrated in breast cancer mortality and are associated with differences in access to care and biologic characteristics. Poor access to care can lead to diagnosis at a more advanced stage, delays in starting treatment, failure to complete treatment, and receipt of inferior chemotherapy regimens. Differences in tumor biology can result in more aggressive cancers, such as those that are negative for estrogen and progesterone receptors as well as human epidermal growth factor receptor 2 (HER2)/neu, so-called triple-negative cancers. Black patients are more likely to be diagnosed with breast cancer that is hormone receptor negative and at a more advanced stage than white patients, and they are more likely to receive inferior care. Hispanics fare better than black patients, but their rate of overall survival seems to be lower than that of non-Hispanic white patients. For more than a decade, a prominent question in health services research has been how to best understand the relative contribution of these different causes of disparities in cancer survival rates, including breast cancer. Differences in treatment patterns have been a major focus of these efforts. Studies have shown that black patients are more likely than white patients to receive treatment that leads to poorer clinical outcomes, including nonstandard adjuvant chemotherapy regimens, first-cycle dose reductions (regardless of body mass index), delays in radiation therapy, and delays in and early termination of chemotherapy. More recently the list of factors known to worsen outcomes for minorities has expanded to include lower levels of English proficiency in some immigrant groups, lower education levels, and poor health literacy. One manifestation is that patients with low levels of English proficiency may be less able to participate in health care decisions, which may affect the treatment that they receive. In the article that accompanies this editorial, Griggs et al have made an important contribution in this latter domain by demonstrating, counterintuitively, that low-acculturated Hispanic patients with breast cancer (those with a strong preference for Spanish compared with English) were the most likely to report having received adjuvant chemotherapy, followed (in order) by high-acculturated Hispanic and non-Hispanic white patients. Adding credence to the finding, Griggs et al found an inverse dose-response relationship between level of acculturation and rate of treatment. Black patients were the least likely to report receipt of chemotherapy, but this difference was not statistically significant. Buttressing the credibility of this finding is that the bulk of the analyses uncovered well-documented associations. The multivariable model showed that clinical cancer-related variables including stage, hormone receptor status, and tumor grade were all associated with receipt of chemotherapy in the direction anticipated. Likewise, younger age and insurance type were associated with receipt of chemotherapy, with Medicaid beneficiaries being the least likely to be treated. Like all studies, this one has some limitations. Participants may not have been representative of the three ethnic groups that were studied within the general population as a result of the study’s sampling strategy and survey-based design. The sampling frame may not be broadly generalizable, given that the patients who were studied were identified through only two SEER registries, those of Los Angeles and Detroit, with Hispanics identified only through the Los Angeles registry. The outcomes of the study were ascertained through a mail survey, a research method that is subject to a variety of biases. Nonresponse bias, a systematic difference in the outcome measured between those who responded to a survey and those who did not, could make treatment rates look higher in patient groups for whom treatment rates are actually lower. This would occur if patients who are less engaged in the health care system are less likely both to receive chemotherapy and to complete a survey about their treatment. Griggs et al also point out that additional details about treatment that were not addressed in their study, which focused only on receipt or nonreceipt of chemotherapy, may contribute to disparities in breast cancer mortality. In addition, rates of HER2/neu amplification and lymphovascular invasion, which are both important biologic factors in decisions regarding chemotherapy administration, could not be examined using this study design. Despite these technical limitations, the results presented in this article raise important questions about the treatment received by Hispanic patients with breast cancer. If Hispanic patients in general, and low-acculturated Hispanic patients in particular, receive more chemotherapy than other groups, why does this not translate into a large-scale survival advantage? One reason could be that the Hispanics who were studied are not representative of the heterogeneous population of Hispanics across the United States. In a recent study using a sample from 17 SEER registries, Puerto Rican Hispanics were found to have a higher risk of breast cancer–specific mortality than white patients, but no difference was found between JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 30 NUMBER 25 SEPTEMBER 1 2012