The Utility of Breast Cancer Index (BCI) Over Clinical Prognostic Tools for Predicting the Need for Extended Endocrine Therapy: A Safety Net Hospital Experience

Introduction: Extended endocrine therapy (EET) benefits select patients with early-stage hormone-receptor positive (HR+) breast cancer (BC) but also incurs side effects and cost. The Clinical Treatment Score at Five Years (CTS5) is a free tool that estimates risks of late relapse in estrogen-receptor positive (ER+) BC using clinicopathologic factors. The Breast Cancer Index (BCI) incorporates 2 genomic assays to estimate late relapse risk and likelihood of benefit from EET. This retrospective study assesses the utility of BCI in selecting EET candidates in a safety net hospital. Materials and Methods: We performed a retrospective chart review on 69 women with early-stage HR+, HER2- BC diagnosed at our institution from December 2009 to February 2016 on whom BCI was submitted. The CTS5 score was also calculated to assess clinical risk of late relapse. Results: Median age was 53 years. All patients included in our analysis had early ER+ HER2-negative BC. Roughly half of the patients (55%) were postmenopausal and 61% were of Hispanic origin. A total of 34 patients (49%) were deemed high-risk (>5%) for late relapse by CTS5, compared to 42 (61%) by BCI. BCI identified 31 (45%) patients that would benefit from EET and of those, 74%% were advised EET. 16 (47%) clinical high-risk patients were advised against EET due to low benefit predicted by BCI. In the clinical low risk group, 9 (26%) were recommended EET based on high benefit predicted by BCI. Conclusion: BCI is reasonable to consider in early-stage HR+ BC and offered clinically relevant information over clinical pathologic information alone.