Secondary Invasive Breast Events among Patients with Hormone-Positive Breast Cancer and High-Risk Oncotype DX Recurrence Scores 26-30 and ≥31

Background: The Oncotype DX Recurrence Score (ODx RS) is the most widely adopted genomic assay used to guide treatment for patients with early-stage, hormone-positive (HR+) breast cancer (BC), with higher scores predicting greater risk of recurrence and benefit from chemotherapy. Patients with ODx RS >25 typically recieve adjuvant chemotherapy; however, data regarding efficacy of chemotherapy for reducing recurrence in this population have been mixed.

Objectives: This study aimed to evaluate outcomes of patients with early-stage HR+ BC with high-risk ODx RS (26-30 and ≥31) in order to assess treatment patterns and outcomes. We hypothesized that the benefit of chemotherapy in these groups may be minimal and that select patients may forgo chemotherapy in favor of more aggressive endocrine therapy and ovarian suppression.

Methods: We performed a retrospective analysis of 515 patients with early-stage, HR+ BC with high-risk ODx RS 26-30 and ≥31 treated between 2006 and 2018. Patients were stratified by RS: low-risk (≤10), intermediate-risk (11-25), and high-risk (≥26). The Kaplan-Meier method was used to estimate the time to secondary invasive breast events (SIBE) or distributions overall and among different RS groups with the log rank test used to compare distributions between groups.

Results: Rates of chemotherapy administration were 7% among the low-risk group, 18% among the intermediate-risk group, and 83% among high-risk patients with 41 SIBE (8%) reported. When stratified by ODx RS, 5-year rates of SIBE were 4%, 6%, and 16% for low-risk, intermediate-risk, and high-risk RS, respectively. Among the 27 lymph node (LN)-negative patients with ODx RS 26-30, 74% received chemotherapy. The 5-year rate of SIBE was 25% among patients who received chemotherapy and 33% among those who did not (p = 0.5489). Among the 23 LN-negative patients with ODx RS ≥31, 91% of patients received chemotherapy. The 5-year rate of SIBE was 0% both with and without chemotherapy.

Conclusions: There was no statistically significant difference in SIBE for patients with high-risk ODx RS based on chemotherapy treatment. More aggressive endocrine therapy with ovarian suppression has become an alternative to chemotherapy among patients with intermediate-risk ODx RS (16-25). This approach may be useful among patients with high-risk ODx RS, with additional studies needed in this patient population.