Groundbreaking genomic test could spare millions of breast cancer patients chemotherapy

A genomic test could allow millions of women with breast cancer to avoid chemotherapy, according to results from an international trial that may reshape treatment guidelines worldwide.

Surgery to remove tumours remains the first step for most patients with breast cancer, the world’s most common cancer. Chemotherapy is frequently recommended afterwards when clinicians judge there is a risk of recurrence, but its toxic side effects — including hair loss, rashes, nausea, insomnia and fatigue — can be physically and emotionally devastating. Some patients also face long term consequences such as infertility, cognitive impairment or early menopause.

The Optima trial, led by University College London and involving more than 4,400 patients in the UK, Norway, Sweden, Australia, New Zealand and Thailand, tested whether a genomic assay can distinguish who truly benefits from chemotherapy. The findings, to be presented at the American Society of Clinical Oncology annual meeting in Chicago, indicate that patients with a low score on the test can be treated with hormone therapy alone with almost identical outcomes to those who received chemotherapy.

The Prosigna test, produced by diagnostics firm Veracyte, measures the activity of 50 genes in tumour tissue to determine molecular subtype and provide a risk score for cancer returning within ten years. In the randomised trial, patients aged 40 and over with hormone positive disease — the most common form, accounting for up to 80% of cases — were allocated either to standard care (chemotherapy followed by hormone therapy) or to a genomics guided pathway. In the latter group, those with a high score received chemotherapy and hormone therapy; those with a low score were treated with hormone therapy alone. Radiotherapy and other treatments were given as appropriate in both arms.

After five years, survival free of breast cancer recurrence was almost identical: 95% in the group that received chemotherapy and hormone therapy, and 94% in those who skipped chemotherapy. The trial therefore suggests that for patients with low Prosigna scores, chemotherapy provides little or no extra benefit and can be safely omitted.

Prof Rob Stein, chief investigator and professor of breast oncology at UCL, said Optima addresses a long standing challenge in breast cancer care by using tumour biology rather than clinical features alone to guide treatment. “Many patients can safely avoid chemotherapy without compromising outcomes,” he said. “This is an important step towards more personalised treatment, sparing individuals the physical and emotional burden of unnecessary toxic therapy and enabling more efficient use of healthcare resources.”

Prof Iain MacPherson, co chief investigator at the University of Glasgow, described the results as “robust, practice changing evidence” that could substantially reduce chemotherapy use for many patients with hormone sensitive disease.

The trial included a small number of men, but too few to draw definitive conclusions for that group. Optima received funding from the National Institute for Health and Care Research (NIHR), Veracyte and cancer charities.

If adopted into routine practice, the test could mark a major shift towards tailored treatment that protects patients from avoidable harm.