The Breast Cancer Index (BCI) is a genomic test used in managing breast cancer. It helps assess the risk of cancer recurrence, particularly several years after initial treatment. This specialized test provides information that aids in personalized treatment decisions, complementing traditional clinical and pathological factors.
Understanding BCI Breast Cancer
The Breast Cancer Index (BCI) is a genomic assay that analyzes specific gene expression patterns within a patient’s tumor tissue. Its primary role is to predict the risk of late distant recurrence, meaning the cancer returns in a distant part of the body more than five years after initial diagnosis. This test is for patients with hormone receptor-positive (HR+), HER2-negative early-stage breast cancer, specifically those with lymph node-negative or limited lymph node involvement (one to three positive nodes).
The BCI test evaluates the expression of 11 specific genes. These genes are grouped into two components: the HOXB13:IL17BR ratio and the Molecular Grade Index (MGI). The HOXB13:IL17BR ratio assesses estrogen signaling, while the MGI, composed of five genes (BUB1B, CENPA, NEK2, RACGAP1, RRM2), evaluates tumor proliferation. These signatures help characterize the tumor’s biology and its potential for late recurrence.
How BCI Testing is Performed
The BCI test uses a small sample of the original tumor tissue, obtained during initial surgery or biopsy. This tissue sample is preserved as a formalin-fixed paraffin-embedded (FFPE) block. From these tumor cells, RNA is extracted in a laboratory.
After RNA extraction, the material undergoes quantitative reverse transcription polymerase chain reaction (RT-PCR) to measure target gene expression levels. The process, from sample receipt to result generation, takes about 7 to 10 days. The oncologist orders and interprets the test, while lab personnel handle tissue processing.
What BCI Results Indicate
BCI provides two distinct pieces of information for a patient’s long-term breast cancer outlook. First, it offers a quantitative estimate of late distant recurrence risk, typically between years 5 and 10 post-diagnosis. This prognostic result categorizes risk as low, intermediate, or high. A low score suggests a minimal chance of late recurrence, while a high score points to a greater probability.
Second, BCI includes a predictive component indicating the likelihood of benefiting from extended endocrine therapy. This result is presented as a “YES” or “NO” answer. A “YES” indicates that continuing hormone therapy beyond the standard five years is likely to further reduce the risk of recurrence. Conversely, a “NO” suggests that extended therapy may not provide significant additional benefit.
How BCI Guides Treatment Decisions
The primary application of BCI is to help patients and their oncologists make informed decisions about the optimal duration of endocrine (hormone) therapy. For patients with hormone receptor-positive, HER2-negative breast cancer, the standard duration of endocrine therapy is often five years. The BCI test helps determine if extending this therapy beyond five years, potentially to ten years, offers a meaningful advantage.
A BCI result indicating a low risk of late recurrence and a low likelihood of benefit from extended therapy may support a decision to discontinue endocrine therapy after the initial five years. This can help patients avoid unnecessary side effects and improve their quality of life. Conversely, a high-risk BCI score, especially when coupled with a high likelihood of benefit from extended therapy, often supports the continuation of endocrine therapy for a longer duration, such as ten years. The National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO) guidelines recognize BCI as a tool to aid these decisions, underscoring its role in personalized breast cancer care.