Genomic risk stratification in breast cancer: A 10-year follow-up of a single-institution prospective cohort comparing Oncotype DX and MammaPrint.

e13083 Background: This study investigates the concordance between the 21-gene recurrence score assay, Oncotype DX (ODX), and the 70-gene signature MammaPrint (MP) in a single academic center and evaluates their correlation with breast cancer outcomes. We previously reported a discordance between MP and ODX results; here, we present a 10-year follow-up survival data. Methods: This prospective cohort study included eighty-six consecutive patients between 2012-2014 with node-negative, hormone receptor-positive breast cancer whose tumor samples were tested using ODX. Based on ODX recurrence scores (RS), patients were treated with either a chemotherapy plus hormonal therapy group or a hormonal therapy-alone group. All patients were per standard practices at our institution. MP was subsequently performed on all samples, classifying patients as either low-risk (MP-L) or high-risk (MP-H). ODX risk classification was defined as intermediate/high risk (ODX-H) for RS ≥ 26 in postmenopausal and ≥ 16 in premenopausal patients (As defined by the TAILORx trial, the addition of chemotherapy to endocrine therapy resulted in an absolute risk reduction of 1.6% in distant recurrence-free survival), and otherwise low risk (ODX-L) (ODX ≤ 26 in postmenopausal or ≤ 15 in premenopausal). Results: In the overall population, the 10-year overall survival (OS), disease recurrence-free survival (DRFS), and breast cancer-free interval (BCFI) were 93%, 91%, and 86%, respectively. Patients classified as ODX-H had lower survival rates (OS: 88%, DRFS: 86%, BCFI: 84%) compared to MP-H patients (OS: 92%, DRFS: 89%, BCFI: 87%). Patients classified as ODX-L had numerically better outcomes than MP-L patients (OS: 100%, DRFS: 97%, BCFI: 89%) compared to (OS: 94%, DRFS: 92%, BCFI: 86%). Approximately 29% of ODX-L patients were classified as MP-H, yet these patients demonstrated favorable long-term outcomes. Conclusions: Despite the limitations of a small sample size, our findings suggest that for patients with node negative hormonal receptor positive breast cancer ODX predicts better prognosis and response to chemotherapy than MP. Future prospective randomized trials directly comparing different genomic assays are warranted to optimize risk stratification and treatment decisions. Breast cancer outcomes based on genomic assay risk classification. Genomic assay / outcomes ODX MP High (n = 51) Low (n = 35) High (n = 37) Low (n = 49) OS 88% 100% 92% 94% DRFS 86% 97% 89% 92% BCFI 84% 89% 87% 86%