For decades, a breast cancer diagnosis with cancer in the lymph nodes meant chemotherapy was almost certain. Doctors knew the treatment was very difficult, but they did not know who truly needed it.
Now they have found an answer. A major trial called OPTIMA has discovered that roughly two-thirds of these high-risk patients can safely avoid chemotherapy completely. The decision is guided by a genetic test that examines 50 genes inside a tumor. The results were presented at the American Society of Clinical Oncology Annual Meeting in Chicago in May 2026, and researchers say they will change medical practice.
The trial was enormous. OPTIMA studied 4,429 patients across six countries: the UK, Norway, Sweden, Australia, New Zealand and Thailand. All had hormone-receptor-positive, HER2-negative early breast cancer, usually with cancer in the lymph nodes under the arm. Normally, all these patients would receive chemotherapy.
Instead, Veracyte's Prosigna test examined their tumors. The test measures 50 genes and produces a risk score. About 68 percent of patients had low scores and received hormone therapy alone. Those with high scores received chemotherapy plus hormone therapy.
The results were important: five-year survival was 94.8 percent for low-score patients receiving both treatments, and 93.6 percent for those receiving hormone therapy alone. This small difference means chemotherapy offered no real benefit for most low-risk patients. The researchers estimate that over 5,000 NHS patients in the UK could avoid chemotherapy each year if this test were used widely.