A genomic test can identify many breast cancer patients who can safely forgo chemotherapy without increasing their risk of recurrence, according to results from the international OPTIMA trial presented at the 2026 American Society of Clinical Oncology meeting. Researchers found that patients aged 40 and over with hormone-sensitive tumors and a low Prosigna test score achieved five-year survival rates comparable to those who received chemotherapy, effectively sparing thousands of patients from unnecessary treatment-related toxicity.
How does the Prosigna test determine treatment?
The Prosigna test measures the activity of genes involved in breast cancer growth using tissue samples from surgery or diagnostic biopsies, according to the OPTIMA (Optimal Personalised Treatment of early breast cancer using Multi-parameter Analysis) research team. By analyzing these biological markers, clinicians can distinguish between tumors that require aggressive systemic treatment and those that respond sufficiently to hormone therapy alone. Lead investigator Professor Rob Stein of the University College London Cancer Institute states that the test allows medical teams to shift away from relying solely on traditional clinical features, such as tumor size or lymph node involvement, toward a model driven by tumor biology.
The OPTIMA trial included 4,429 patients across the UK, Norway, Sweden, Australia, New Zealand, and Thailand. Unlike previous studies that focused heavily on postmenopausal women with limited lymph node involvement, this trial included premenopausal women and those with more extensive disease.
What were the survival outcomes for patients?
Data from the trial shows that 68% of participants received a low Prosigna score, indicating a low risk of recurrence. For this specific group, the five-year survival rate was 94.9% for those who received chemotherapy and 95.1% for those who did not. According to the study’s statistical analysis, at most 2% of patients with a low score would see any benefit from chemotherapy, suggesting the treatment provides little to no additional protection for the vast majority of this population. Professor Iain MacPherson of the University of Glasgow notes that these findings provide robust, practice-changing evidence that chemotherapy use can be safely reduced.
Case Study: A patient’s experience with genomic testing
Karen Bonham, a 64-year-old speech and language therapist from Cardiff, was diagnosed with hormone-sensitive breast cancer in 2017. Despite standard clinical guidelines suggesting chemotherapy for her specific diagnosis—which included two affected lymph nodes—the Prosigna test results arrived just days before her scheduled treatment. Because her test indicated a low score, Bonham was assigned to the trial’s test-directed group. She avoided chemotherapy entirely, opting instead for radiotherapy and hormone therapy. Almost nine years later, Bonham remains cancer-free, attributing her quality of life to the ability to receive targeted, appropriate treatment rather than a one-size-fits-all regimen.
What is the future of genomic testing in the NHS?
Healthcare bodies, including the National Institute for Health and Care Excellence (NICE), are expected to use these findings to evaluate wider access to Prosigna testing. By demonstrating the cost-effectiveness of test-directed treatment, the trial provides a pathway for the National Health Service (NHS) to reduce unnecessary chemotherapy for an estimated 5,000 patients annually. While the current results are comprehensive, researchers noted that it is not yet known if these findings apply to patients under the age of 40. The next phase of the trial is designed to generate data specifically for this younger demographic.
If you or a loved one are facing a breast cancer diagnosis, ask your oncologist if genomic testing is appropriate for your specific tumor profile. Understanding the biological activity of the cancer can often help patients and doctors make more informed decisions about the necessity of systemic therapies.
Frequently Asked Questions
- Who is eligible for the Prosigna test? The OPTIMA trial results apply to patients aged 40 and older with hormone-sensitive breast cancer.
- Does the test work for patients with lymph node involvement? Yes. The trial successfully demonstrated that outcomes were similar regardless of the number of affected lymph nodes.
- Is chemotherapy always necessary for breast cancer? No. According to the OPTIMA trial, many patients with low genomic scores can safely avoid chemotherapy without compromising their survival outcomes.
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