Genomic Test Helps Early Breast Cancer Patients Avoid Chemotherapy

Adjuvant chemotherapy decisions in early breast cancer can expose many patients to toxicities without clear benefit when clinical factors alone do not precisely predict recurrence risk. Clinicians therefore seek molecular tools that better stratify risk and support safe de-escalation. Large, prospective evidence is essential to guide treatment while preserving outcomes across diverse patient groups. New findings demonstrate that a genomic assay can personalize chemotherapy decisions and spare many patients treatment without compromising disease control.

At UNC Health (Chapel Hill, NC, USA), investigators highlight Prosigna, a genomic test marketed by Veracyte (South San Francisco, CA, USA) that stratifies risk in early-stage breast cancer. The assay analyzes tumor samples and applies a machine learning algorithm to generate a Risk of Recurrence (ROR) score that estimates the likelihood of relapse within 10 years. This score is intended to inform whether chemotherapy is necessary or whether endocrine therapy alone is sufficient.

Prosigna’s use was evaluated in the Optimal Personalized Treatment of early breast cancer using Multi-parameter Analysis (OPTIMA) trial. Launched in 2007, OPTIMA enrolled more than 4,400 patients with early-stage, estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer across the United Kingdom, Norway, Sweden, Australia, New Zealand, and Thailand over 20 years. Results were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago. The median follow-up was 4.0 years, and the reported cohort included 4,429 patients.

Treatment allocation in OPTIMA was guided by the Prosigna ROR threshold. Patients with ROR scores greater than 60 received chemotherapy followed by hormone therapy, while those with ROR scores of 60 or lower received hormone therapy alone. Findings showed that 68% of clinically high-risk patients could safely omit chemotherapy, with a five-year cancer-free survival rate of 93.7% among those managed without chemotherapy. The test performed equally well in premenopausal women and in patients with multiple positive lymph nodes. Investigators characterized the evidence as Level 1A, indicating the highest level of prospective validation in this setting. The announcement noted that oncologists in the United States and the United Kingdom can order the assay.

“Prosigna owes its success to patients who trusted the study and their physicians, companies providing cutting-edge technologies for molecular testing, and researchers and clinicians turning ideas into diagnostics to improve patient care,” said Charles Perou, Ph.D., distinguished professor at the UNC School of Medicine and an expert on breast cancer genomics at UNC Lineberger Comprehensive Cancer Center.

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