Findings from the OPTIMA trial show that the Prosigna test identifies patients who can safely skip chemotherapy and use hormone therapy alone.
Results from the international OPTIMA trial indicate that a genomic test can identify many breast cancer patients who can safely avoid chemotherapy without increasing the risk of recurrence.
The findings, presented at the 2026 American Society of Clinical Oncology meeting, suggest that patients aged 40 and over with hormone-sensitive tumors and a low Prosigna test score can be treated with hormone therapy alone. Researchers estimate that more than 5,000 National Health Service (NHS) patients per year could avoid chemotherapy based on these results.
The OPTIMA trial (Optimal Personalised Treatment of early breast cancer using Multi-parameter Analysis) used a genomic test from Veracyte called Prosigna to measure the activity of genes involved in breast cancer growth. The test is performed on cancer tissue samples from surgery or diagnostic needle biopsies and can be run by NHS laboratories.
“OPTIMA addresses a long-standing challenge in breast cancer care: identifying who truly benefits from chemotherapy and who does not. Our findings show that many patients can safely avoid chemotherapy without compromising their outcomes,” says Rob Stein, chief investigator of the OPTIMA trial and professor of breast oncology at the University College London Cancer Institute, in a release.
Trial Data and Patient Outcomes
The trial followed 4,429 patients across the UK, Norway, Sweden, Australia, New Zealand, and Thailand. Participants were aged 40 or older and had been diagnosed with hormone-sensitive breast cancer that had often spread to the lymph nodes.
Of the participants, 68% had a low Prosigna score. For this group, five-year survival rates were 94.9% for those who received chemotherapy and 95.1% for those who did not. A statistical analysis showed that at most 2% of patients with a low score would benefit from chemotherapy, suggesting the treatment offers little to no additional benefit for this population.
“These results mark an important and significant step toward more personalised treatment. The trial has successfully used tumour biology to guide decisions rather than relying solely on traditional clinical features,” says Stein in a release.
Expanding the Scope of Genomic Testing
Unlike previous studies that focused primarily on postmenopausal women with limited lymph node involvement, OPTIMA included premenopausal women and patients with more extensive disease. Outcomes were similar for both pre- and postmenopausal women, and no differences were observed based on the number of affected lymph nodes.
“OPTIMA provides robust, practice-changing evidence that we can safely reduce the use of chemotherapy for many patients with hormone-sensitive breast cancer,” says Iain MacPherson, co-chief investigator and professor of breast oncology at the University of Glasgow, in a release. “These findings represent a major step forward in delivering more personalised, precise care, ensuring that treatment decisions are driven by what will genuinely improve outcomes for patients, while avoiding unnecessary toxicity.”
The research team noted it is not yet known if the findings apply to patients under the age of 40. The next phase of the trial aims to generate further information regarding test use for this younger demographic.
The results will be used to inform decision-making by healthcare bodies, including the National Institute for Health and Care Excellence (NICE), regarding wider access to Prosigna testing by demonstrating the cost-effectiveness of test-directed treatment.
Patient’s story
Karen Bonham, 64, from Cardiff, was diagnosed with breast cancer after attending routine screening in June 2017. Married with two children, Karen had worked as a speech and language therapist for 40 years
She was recalled to the breast clinic at Velindre Cancer Centre in Cardiff within two weeks of screening, where a biopsy confirmed left-sided breast cancer. Karen underwent a left mastectomy and axillary node clearance in July 2017. Results showed a large (>5cm) but slowly growing hormone-sensitive cancer with two affected lymph nodes. Chemotherapy is the standard treatment for this type of breast cancer.
Bonham became aware of the OPTIMA trial during one of her first oncology appointments in September 2017 while discussing the possibility of chemotherapy, a treatment she was dreading. Bonham told her doctors she was interested in being a part of new research that could support patient outcomes, and dared to hope she would not need chemotherapy.
The Prosigna test was carried out on tissue stored from Bonham’s breast surgery while plans were already being made for standard chemotherapy to begin. Bonham said she was only days away from starting treatment and had “already cut my hair short” when the results came back just over two weeks later.
While walking on a local beach, Bonham received a phone call from her hospital telling her she’d been allocated to the test-directed group of the trial and did not require chemotherapy.
She says in a release, “How to describe the initial feeling? Immense relief? Like Christmas? Certainly a mixture of the two.”
Instead of chemotherapy, Bonham went on to receive radiotherapy and hormone therapy, completing eight years of active treatment.
Now almost nine years on from her diagnosis, Bonham says she does not feel defined by cancer and has returned to normal family life. She remains active, enjoying walking and yoga, and says taking part in the OPTIMA trial “helped decision making to allow me to receive targeted, appropriate treatment more quickly and has enabled my positive health outcome.”
Photo caption: OPTIMA patient Karen Bonham
Photo credit: Karen Bonham
