Breast Cancer with Low Recurrence Score on Oncotype DX©: Interplay Between Early Recurrence, Lobular Histology and BRCA Mutation.

INTRODUCTION: The 21-gene recurrence score assay Oncotype DX© (ODX) has clear prognostic and predictive value regarding adjuvant chemotherapy. However, recent studies have shown the clinical distinctiveness of both BRCA1/2-driven early breast cancer (EBC) and invasive lobular (ILC) breast cancers. We evaluated the association between BRCA1/2-driven EBC/ILC and Oncotype DX failure despite a recurrence score ≤ 20.
METHODS: Here, we describe a small cohort of 16 patients from our center who, despite a low recurrence score (RS) ≤ 20, suffered from early disease recurrence. Clinical parameters of our cohort of patients were compared to a cohort from the general population of Clalit Health Service (CHS).
RESULTS: Median age at diagnosis in our cohort was significantly younger. BRCA mutational status was available in 14 patients in our cohort. A high percentage of these patients had BRCA1/2 mutations (35.7%), either germline (in 3) or somatic (in 2). Half of our cohort was diagnosed with lobular carcinoma (ILC) relative to 10-15% in the general population of BC (p = 0.02). The median time to recurrence was 44 months.
CONCLUSION: BRCA1/2 mutation and ILC are highly represented in this cohort. Although our cohort is small, these data may suggest that a RS ≤ 20 in these subgroups may not reflect a low risk of recurrence.