Dr Diab on the Clinical Relevance of the Breast Cancer Index in HR+ Early-Stage Disease

“The BCI goes above what we traditionally consider regarding [tumor] size, [tumor] grade, [and] number of lymph nodes. It adds more value in terms of distinguishing which patients would [and] would not benefit from extended adjuvant therapy.”

Sami Diab, MD, medical director of the Center for Cancer and Blood Research at the Pagosa Springs Medical Center, discussed the clinical utility of the Breast Cancer Index (BCI) test as a foundational tool for guiding shared decision-making regarding the duration of extended adjuvant hormonal therapy in patients with early-stage, hormone receptor (HR)–positive breast cancer.

Diab emphasized that determining the optimal length of hormonal therapy in patients with HR-positive breast cancer after completion of the initial, recommended 5 years of this treatment represents a critical juncture for both patients and oncologists, often necessitating a complex evaluation of long-term risks and benefits. Rather than relying on subjective clinical judgment, Diab argued for a rigorous, data-driven approach to ensure that medical recommendations are grounded in objective genomic evidence rather than clinical intuition. The BCI is the only genomic test supported by both the National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology and the ASCO Clinical Practice Guidelines for assisting in the decision-making process for extended adjuvant breast cancer therapy.

To further explore the real-world effect and practical application of this tool, the observational BCI Registry study (NCT04875351) was launched, eventually enrolling a cohort of 3005 patients. The primary objective of this large-scale registry was to observe how the test results influenced the clinical behavior of oncologists and the treatment choices of their patients in daily practice settings. Data from the study revealed that 41.2% of oncologists changed their original treatment recommendations regarding the prescription of extended adjuvant therapy, based on insights provided by the BCI.

This shift in practice patterns shows that the BCI provides clinical insights that transcend traditional prognostic factors, such as tumor size, histological grade, and number of positive lymph nodes, Diab explained. Ultimately, Diab concluded that the test adds essential value by distinguishing which patients will derive a therapeutic benefit from continuing hormonal therapy beyond the initial 5-year mark vs those who could safely discontinue treatment without compromising their long-term outcomes.