In a study reported in the Journal of the National Cancer Institute, Benefield et al found that black women with borderline estrogen receptor (ER)-positive breast cancer had significantly poorer disease-free interval compared with those with ER-positive disease, irrespective of whether they received endocrine therapy.

The study included 2,859 women from the Carolina Breast Cancer study, including 1,509 white women and 1,350 black women. Among these, 7.6% (n = 217) had ER-borderline disease (≥ 1% to < 10% positivity), 26.5% had ER-negative disease, and 65.9% had ER-positive disease. Among the 217 women with ER-borderline disease, 118 were white and 99 were black.

Estrogen Receptor Status and Disease-Free Interval  

ER-borderline cases were more frequently basal-like (relative frequency difference = +37.7%, 95% confidence interval [CI] = 27.1–48.4) and had high PAM50 subtype and risk-of-recurrence score (relative frequency difference = +52.4%, 95% CI = 36.8–68.0) vs ER-positive cases. Presence of a high risk-of-recurrence score, ER-borderline tumor was significantly associated with black race (relative frequency difference = +26.2%, 95% CI = 9.0–43.3).

Among all women, 5-year disease-free interval rates were 93.7% for those with ER-positive disease vs 88.2% for ER-borderline patients who received endocrine therapy (P = .32), 77.3% for ER-borderline patients without endocrine therapy (P <.001), and 80.7% for ER-negative patients (P < .001). In analysis adjusting for age, disease stage, and receipt of chemotherapy, compared with ER-positive patients, the hazard ratio for recurrence was 2.03 (95% CI = 0.89–4.65) among ER-borderline patients with endocrine therapy and 3.33 (95% CI = 1.84–6.02) among ER-borderline patients without endocrine therapy.

Compared with white women with ER-positive disease, hazard ratios for recurrence were 0.99 (95% CI = 0.14–7.19) for white women with ER-borderline disease with endocrine therapy and 4.22 (95% CI = 1.75–10.23) among those with ER-borderline disease without endocrine therapy.

Compared with black women with ER-positive disease, hazard ratios for recurrence were 2.77 (95% CI = 1.09–7.04) for those with ER-borderline disease with endocrine therapy and 2.53 (95% CI = 1.13–5.70) among those with ER-borderline disease without endocrine therapy.

The investigators concluded, “ER-borderline tumors were genomically heterogeneous with survival outcomes that differed by endocrine therapy receipt and race. Black race predicted high-risk ER-borderlines and may be associated with poorer endocrine therapy response.”

Melissa A. Troester, PhD, of the Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, is the corresponding author for the Journal of the National Cancer Institute article.

Disclosure: The study was supported by the UNC Lineberger Comprehensive Cancer Center (funded by the University Cancer Research Fund), Susan G. Komen Foundation, National Cancer Institute, and National Institutes of Health. For full disclosures of the study authors, visit academic.oup.com.