摘要：We examined the current literature to understand factors that influence endocrine therapy (ET) adherence among racial/ethnic and socioeconomic subpopulations of breast cancer patients. We searched PubMed and PsycINFO databases for studies from January 1, 1978, to June 20, 2014, and January 1, 1991, to June 20, 2014, respectively, and hand-searched articles from relevant literature reviews. We abstracted and synthesized results within a social ecological framework. Fourteen articles met all inclusion criteria. The majority of included articles reported significant underuse of ET among minority and low-income women. Modifiable intrapersonal, interpersonal, and community-level factors are associated with ET use, and these factors vary across subgroups. Both race/ethnicity and socioeconomic status are associated with ET use in most settings. Variation in factors associated with ET use across subgroups indicates the need for more nuanced research and targeted interventions among breast cancer patients. Low medication adherence is common among patients taking oral drugs; an estimated half of all patients are nonadherent to a medication regimen across multiple chronic disease areas. 1 This low medication adherence is problematic because it is associated with poorer prognosis for many common conditions. 2 Evidence has demonstrated that non-White patients are less likely to adhere to medication regimens than White patients, 3,4 suggesting that medication adherence may be an important lever for targeting racial disparities in health care outcomes. Medication adherence has become a particularly important issue in cancer care because the use of oral anticancer drugs in clinical practice has increased. 3 Endocrine therapy (ET) for breast cancer is among the most common oral anticancer therapies, and racial variation in ET adherence may play a role in racial disparities in breast cancer care outcomes. Breast cancer is the most common cancer among women in the United States: of the 232 570 women diagnosed with invasive breast cancer each year, approximately three quarters will have hormone receptor–positive breast cancer. 5,6 Typically, women with this type of breast cancer undergo surgery with or without radiation, some will take adjuvant chemotherapy, and nearly all will be eligible for ET. 7,8 ET is most commonly given in the adjuvant setting to prevent recurrence of curable cancers. 5,9 ET consisting of at least a 5-year course of tamoxifen or an aromatase inhibitor (AI), is the gold standard for adjuvant treatment of these cancers, and it reduces 5-year breast cancer recurrence by 40% and breast cancer mortality by one third. 10 However, evidence from observational and patient-reported sources has suggested that many women underuse ET because of noninitiation (i.e., never starting ET), nonadherence (i.e., not taking ET as prescribed), or nonpersistence (i.e., not taking ET for the recommended duration). 11–15 ET underuse is associated with shorter time to recurrence, lower quality of life, and increased medical costs. 16 Approximately one third of women who initiate adjuvant tamoxifen discontinue the drug before the 5-year, guideline-recommended duration. 12,13,15 Of those who continue taking tamoxifen, 16% to 28% do not fully adhere to the therapy. 12,13,17–19 Furthermore, adherence and persistence decline over time. 19 Thus, by the end of the 5-year course of therapy, only about half of women have taken tamoxifen as prescribed. 12,13 AI data have shown similar patterns of underutilization; 12 at 5 years, 19% to 25% of women have discontinued their AI, 20,21 and 20% to 31% of women have been nonadherent. 18,22 Minority populations may be disproportionately affected by ET noninitiation, discontinuation, and nonadherence. 12,23–28 Minority and low-income populations are less likely to be integrated into the health care system; thus, they may face unique barriers to care, such as poor access to providers, that influence receipt of ET and other cancer-related treatment. 29,30 Among minority women who are also low income or who experience high levels of social stressors, competing social and economic demands may take priority over medication adherence, leading to suboptimal medication use. 31 Patterns of ET utilization among minority women are understudied and may contribute to the well-recognized and persistent racial, ethnic, and socioeconomic disparities in outcomes. Despite advances in breast cancer prevention and treatment, breast cancer mortality remains 37% higher among Black women than among White women. 32 Biological differences are important but cannot fully explain this racial/ethnic variation in mortality. 9,33 Thus, the observed disparities likely arise from a combination of factors, including incomplete or omitted ET treatment. In several studies of insured women, non-White race 11,12,22,24–28 and low socioeconomic status (SES) 34 have been associated with lower ET initiation, adherence, and persistence; however, reasons for this variation have not been well described. Although previous literature reviews have described factors that are associated with ET utilization broadly, none have detailed racial variation in the use of ET. We addressed this literature gap by conducting a systematic review of the adjuvant ET literature that is focused on barriers to ET use among low-income and minority populations.
