A novel Breast Cancer Index for prediction of distant recurrence in HR+ early stage breast cancer with 1 to 3 positive nodes

Purpose: Study objective was to characterize the prognostic performance of a novel Breast Cancer Index model (BCIN+), an integration of BCI gene expression, tumor size, and grade, specifically developed for assessment of distant recurrence (DR) risk in HR+ breast cancer patients with 1-3 positive lymph nodes (pN1). <br><br> Experimental Design: Analysis was conducted in a well-annotated retrospective series of pN1 patients (N=402) treated with adjuvant endocrine therapy with or without chemotherapy using a pre-specified model. The primary endpoint was time-to-DR. Results were determined blinded to clinical outcome. Kaplan-Meier estimates of overall (0-15y) and late (≥5y) DR, hazard ratios and 95% CIs were estimated. Likelihood ratio statistics assessed relative contributions of prognostic information. <br><br> Results: BCIN+ classified 81 patients (20%) as low risk with a 15-year DR rate of 1.3% (95%CI: 0.0-3.7%) vs 321 patients as high risk with a DR rate of 29.0% (23.2-34.4%). In patients DR-free for ≥5y (n=349), the late DR rate was 1.3% (95%CI: 0.0-3.7%) and 16.1% (10.6-21.3%) in low- and high-risk groups, respectively. BCI gene expression alone was significantly prognostic (LR-2=20.12, P<0.0001). Addition of tumor size (LR-2=13.29, P=0.0003) and grade (LR-2=12.72, P=0.0004) significantly improved prognostic performance. BCI added significant prognostic information to tumor size (LR-2=17.55, P<0.0001); addition to tumor grade was incremental (LR-2=2.38, P=0.1) with considerable overlap between prognostic values (LR-2=17.74). <br><br> Conclusions: The integrated BCIN+ identified 20% of pN1 patients with limited risk of recurrence over 15y, in whom extended endocrine treatment may be spared. Ongoing studies will characterize combined clinical-genomic risk assessment in node-positive patients.

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