Genomic Test Changed Breast Cancer Treatment Decisions

A test for early-stage patients helped physicians personalize decisions on extending hormone-blocking therapy.

Updated on Sept. 28, 2026 in Cancer

A close-up view of a glass laboratory pipette on a clean metal surface, highlighting the precision of genomic diagnostic testing. — A study published this week demonstrates that genomic testing using the Breast Cancer Index significantly alters long-term treatment strategies for early-stage breast cancer patients. AI Illustration. Upload story photo >

Live Poll

Would you choose genomic testing to potentially avoid years of additional medical treatment and side effects?

A large study found that using a genomic test, the Breast Cancer Index, altered long-term treatment plans for 42% of patients with early-stage breast cancer. The findings suggest the test can help clarify the necessity of endocrine therapy for individuals navigating the risk of late recurrence.

Why it matters

Standard clinical markers like tumor grade can leave uncertainty about whether to continue hormone-blocking therapy, a process many patients find difficult due to persistent side effects. This genomic approach provides a clearer picture of whether extending treatment actually provides a benefit.

In a study of nearly 3,000 patients, the Breast Cancer Index genomic test changed therapy recommendations for 42% of participants. The registry data indicates that in two-thirds of these cases, the test result led physicians to recommend stopping extended endocrine therapy.

The players

Sarah Cannon Research Institute

A research organization that conducts global clinical trials focusing on oncology and cancer care innovations.

Hartford HealthCare

A healthcare system affiliated with the lead study authors that oversees clinical oncology research.

NCCN

The National Comprehensive Cancer Network provides evidence-based clinical practice guidelines used by oncologists worldwide.

ASCO

The American Society of Clinical Oncology is a professional organization that sets standards and guidelines for cancer treatment and research.

The details

The Breast Cancer Index test analyzes genomic signatures to predict the likelihood of late recurrence in HR-positive breast cancer. Because endocrine therapy works by limiting the hormones that fuel tumor growth, it is often prescribed long-term to prevent recurrence. However, with 50% of recurrences occurring after five years and 83% of patients reporting side effects, the test helps determine if the risk of cancer returning outweighs the burden of ongoing medication.

July 2026: An updated BCI report option providing 10-year recurrence risk context launched.
September 28, 2026: Study findings were published in JAMA Network Open.

Health Landscape

This study aligns with the broader integration of genomic testing into the standard of care for breast cancer treatment. It reflects a shift toward precision medicine, where clinicians move beyond standard tumor staging to use molecular data to guide the duration of endocrine therapy.

If you are managing HR-positive breast cancer, it is worth discussing with your doctor whether genomic testing is appropriate for your specific stage of care. This is especially relevant if you are concerned about side effects or are considering whether to continue or stop endocrine therapy.

The takeaway

Genomic testing can provide vital data when deciding whether to continue long-term hormone-blocking therapies. Always talk to your oncologist about your specific recurrence risk and whether a genomic test could help tailor your treatment plan to your body's needs.