Community clinical practice patterns and mortality in patients with intermediate oncotype DX recurrence scores: Who benefits from chemotherapy?

BACKGROUND: The Oncotype DX recurrence score (RS) is used as a tool for making decisions about chemotherapy for patients who have hormone receptor (estrogen receptor or progesterone receptor)-positive, HER2-negative breast cancer. There is no benefit from chemotherapy among patients aged ≥50 years who have lymph node-negative disease and an RS from 11 to 25, but the benefit of chemotherapy in the lymph node-positive group remains unknown. METHODS: On the basis of data from the National Cancer Data Base between 2010 and 2014, a nationwide, retrospective cohort study included 73,185 women who had stage I through IIIA breast cancer and an RS between 11 and 30. RESULTS: Receipt of chemotherapy was associated with a reduced risk of death among patients who had lymph node-positive breast cancer (hazard ratio [HR] 0.58; 95% confidence interval [CI], 0.45-0.74; P < .001) after adjusting for other prognostic factors in a multivariable Cox model. The 5-year survival gain ranged from 1.3% (RS 11-17 subgroup), to 3.3% (RS 18-25 subgroup), and to 6.7% (RS 26-30 subgroup). Among patients who had lymph node-negative disease, chemotherapy was associated with a reduced risk of death for those with an RS from 25 to 30 (HR, 0.68; 95% CI, 0.48-0.96; P = .03; 5-year survival gain, 1.8%), but there was no benefit from chemotherapy for patients who had an RS from 11 to 17 (HR, 0.97; 95% CI, 0.61-1.55; P = .90), and there was a marginally significant benefit for women who had an RS from 18 to 25 (HR, 0.79; 95% CI, 0.62-1.00; P = .05). Similar results were observed using propensity score-matching method. CONCLUSIONS: The benefit of chemotherapy for patients with breast cancer who have an intermediate RS is driven in a nonlinear fashion by RS: the higher the RS, the larger the absolute benefit. Findings from this study underscore the utility of real-world data to inform joint decision making in practice.