As part of a multi-pronged research effort to understand why breast cancer mortality is higher among black women, University of North Carolina Lineberger Comprehensive Cancer Center researchers found that adherence to breast cancer medications may play a role in the disparity.
In the Journal of the National Cancer Institute, researchers published findings that black women were more likely than white women to report not taking endocrine therapy for breast cancer as prescribed, although women of both races reported similar rates of discontinuing the medication. For women with hormone receptor-positive breast cancer, taking endocrine therapy for up to 10 years can reduce the risk of cancer recurrence, and of cancer-related death.
“Women need to maintain adherence for endocrine therapy to have its intended effect,” said UNC Lineberger’s Stephanie Wheeler, PhD, MPH, associate professor in the UNC Gillings School of Global Public Health. “We need to think about motivation and risk trade-offs, and helping women in the daily process of taking this medication, and developing culturally-tailored interventions to specifically target black women’s needs.”
Studies have shown that breast cancer mortality is 41.5 percent higher among black women compared to white women. Despite the benefits of endocrine therapy for hormone-receptor positive breast cancer, between 15 and 49 percent of women with hormone receptor positive breast cancer never start endocrine therapy, and more than half do not take it as recommended.
Using data from the Carolina Breast Cancer Study, a multi-phase study designed to understand breast cancer in black and white women in North Carolina, the researchers studied non-adherence, which was defined as self-reporting not taking endocrine therapy or missing more than two pills in a two-week period, and discontinuation. They surveyed 1,280 women aged 20 to 74 years with a first primary stage I-III, hormone receptor-positive breast cancer.
Black women in the study more often reported non-adherence, at 13.7 percent, compared with 5.2 percent of white women. Black and white women had similar rates of discontinuation, at 10 and 10.7 percent, respectively.
“This means that almost one in four black women and 16 percent of white women are not taking their endocrine therapy as prescribed, and therefore, not receiving the benefits,” Wheeler said. “Incomplete use of guideline-recommended treatment is one of the factors that could contribute to mortality differences by race.”
Black women also more often reported having burdensome side effects, including hot flashes, night sweats, breast sensitivity and joint pain; believing their risk of cancer returning would not change if they stopped endocrine therapy; forgetting to take the mediation; and cost-related barriers.
“One of the strongest factors contributing to non-adherence was what we called ‘ambivalence’ about the benefits of endocrine therapy, which was when women did not think that non-adherence would change their risk of cancer recurrence,” Wheeler said. “This seemed to be the largest predictor of non-adherence and discontinuation across both white and black women.”
However, after adjusting for side effect variation and socioeconomic status, they found black women were still more likely to report missing medications. Wheeler said UNC Lineberger researchers are working on an intervention to help motivate and encourage women to take their endocrine therapy that is targeted to women’s specific needs. She also said improving women’s understanding of the importance of endocrine therapy in preventing breast cancer recurrence will be critical.
“I think what is compelling to me, as a clinician treating breast cancer patients, is that adherence is impacted most dramatically not just by side effects, but by women’s beliefs about the likelihood that their cancer may return, and how much they believe their endocrine therapy medication will protect them from that recurrence,” said UNC Lineberger’s Katherine Reeder-Hayes, MD, MBA, assistant professor in the UNC School of Medicine Division of Hematology/Oncology. “These are beliefs we may be able to influence in the clinic, particularly if we focus on at-risk women, including minorities, with appropriate communication and shared decision making. It may be easier to put up with side effects if you understand the benefits you’re getting, and feel positive about your decision to take this treatment.”
In addition to Wheeler and Reeder-Hayes, the other authors are Jennifer Spencer, MSPH, Jo Anne Earp, ScD, Andrew Olshan, PhD, Mary E. Bell, and Morris Weinberger, PhD, UNC Gillings and UNC Lineberger; Laura C. Pinheiro, MPH, PhD, Weill Cornell Medical College, New York; Caitlin C. Murphy, PhD, University of Texas Southwestern Medical Center, Dallas; Lisa Carey, MD, UNC Lineberger; and Chiu Kit Tse, UNC Gillings.
The study was supported by an American Cancer Society Mentored Research Scholar Grant, the University Cancer Research Fund, the National Cancer Institute, and Susan B. Komen.