Genomic assays such as Oncotype Dx (ODX) and MammaPrint are used for risk-adapted treatment decisions among patients with early breast cancer. However, to the authors' knowledge, concordance between genomic assays is modest. Using real-world data, the authors performed a comparative analysis of ODX and MammaPrint.

A cohort of women diagnosed with early-stage, hormone receptor-positive breast cancer who received ODX or MammaPrint was established using the National Cancer Data Base (NCDB) for 2010 through 2016. Using the propensity score matching method, 2 groups of patients with similar clinical and demographic characteristics were defined: one group received ODX and the other received MammaPrint. The authors examined the association between use of the ODX or MammaPrint assays and overall survival using Cox models.

Of the 451,693 eligible patients, approximately 45.3% received ODX and 1.8% received MammaPrint testing. The use of ODX increased from 36.1% in 2010 to 49.9% in 2016, whereas use of MammaPrint increased from 0.5% in 2010 to 3.3% in 2016. The authors matched 5042 patients who received ODX with 5042 patients who received MammaPrint. The 5-year risks of death for the MammaPrint low-risk group and the ODX low-risk group were 3.4% and 4.7%, respectively. The prognostic value of MammaPrint was similar to that of ODX; the C-index was 0.614 (95% confidence interval, 0.572-0.657) for MammaPrint and 0.581 (95% confidence interval, 0.530-0.631) for ODX. There was a difference in the performance of the ODX assay observed across racial and/or ethnic groups (P < .001), with a slightly better performance noted among white compared with African American and Hispanic individuals.

Both the ODX and MammaPrint tests are good at identifying low-risk individuals who could be spared chemotherapy. The suboptimal performance of ODX in ethnic minority individuals deserves further investigation.