In a U.S. population–based cohort study reported in JAMA Oncology, Hoskins et al found that among patients with estrogen receptor–positive breast cancer, Black women were more likely than White women to have a high Oncotype DX 21-gene recurrence score. Researchers also found that breast cancer–specific mortality was higher in Black vs White women with axillary node–negative tumors in each recurrence score stratum.

Study Details

In the study, the Surveillance, Epidemiology, and End Results Oncotype DX 2004–2015 database was used to obtain breast cancer–specific survival data on women aged ≥ 18 years diagnosed with first primary stage I to III estrogen receptor–positive breast cancer between January 2004 and December 2015 and had tumor testing through the Genomic Health Clinical Laboratory. The primary outcome measure was breast cancer–specific mortality among different racial/ethnic groups stratified by the 21-gene recurrence score risk categories.

Key Findings

Among 86,033 women included in the analysis, 64,069 (74.4%) were White; 6,719 (7.8%) were Black; 7,944 (9.2%) were Hispanic; 6,950 (8.0%) were Asian/Pacific Islander; and 351 (0.4%) were American Indian/Alaska Native. A total of 74,002 (85.6%) had axillary node–negative tumors.

Black women were more likely vs White women to have recurrence score > 25 (17.7% vs 13.7%, P < .001). In a model adjusting for age, year of diagnosis, tumor size, and nodal status, rate ratios for recurrence score > 25 were significantly higher for Black women (1.21, P < .001) and American Indian/Alaska Native women (1.36, P = .009) vs White women.

Cumulative hazards for breast cancer–specific mortality differed among racial/ethnic groups for recurrence score 0 to 10 (overall P = .004), 1 to 25 (P < .001), and > 25 (P = .03) among all women and for recurrence score 0 to 10 (P = .002), 11 to 25 (P < .001), and > 25 (P = .04) among those with axillary node–negative disease.

Kent F. Hoskins, MD

In analysis adjusted for age, tumor characteristics, and treatment, significantly increased risk of breast cancer–specific mortality was found for Black women vs White women with axillary node–negative disease in each recurrence score risk stratum: subdistribution hazard ratios were 2.54 (95% confidence interval [CI] =1.44–4.50) for recurrence score 0 to 10, 1.64 (95% CI = 1.23–2.18) for recurrence score 11 to 25, and 1.48 (95% CI = 1.10–1.98) for recurrence score > 25. No significant differences vs White women were found for any other group.

The prognostic accuracy of the recurrence score among patients with axillary node–negative disease was significantly lower (P = .002) for Black vs White women, with C index values of 0.656 (95% CI = 0.592–0.720) vs 0.700 (95% CI = 0.677–0.722).

The investigators concluded: “In this cohort study, Black women in the U.S. were more likely to have a high-risk recurrence score and to die of axillary node–negative breast cancer compared with non-Hispanic White women with comparable recurrence scores. The Oncotype DX Breast Recurrence Score test has lower prognostic accuracy in Black women, suggesting that genomic assays used to identify candidates for adjuvant chemotherapy may require model calibration in populations with greater racial/ethnic diversity.”

Kent F. Hoskins, MD, of the Division of Hematology and Oncology, University of Illinois at Chicago, is the corresponding author for the JAMA Oncology article.

Disclosure: The study was supported by a grant from the National Center for Advancing Translational Sciences, National Institutes of Health. For full disclosures of the study authors, visit ascopubs.org.