Breast Cancer Index (BCI) prognostic and predictive classification in older versus younger patients with early-stage HR+ breast cancer (BC) and correlation with clinical risk factors.

546Background: Older patients with HR+ BC may present distinct challenges for treatment decision-making. BCI is a validated gene expression assay for pts with early stage HR+ BC that provides 2 results: BCI Predictive, based on HoxB13/IL17BR (H/I ratio), reports a prediction of likelihood of benefit from extended endocrine therapy (EET); BCI Prognostic, based on the combination of H/I and proliferation-based genes, reports individualized risk of late distant recurrence (DR). Here, the predictive and prognostic value of BCI results across the aging spectrum ( 50 clinicopathologic and molecular variables from cases submitted for BCI in clinical practice (N = 14,463). Clinicopathologic variables were abstracted from pathology reports, and were available for a subset of cases. Chi-squared tests were used to compare B...