Millions of women with breast cancer could be spared chemotherapy thanks to a novel genomic test, according to the results of an international trial that could transform healthcare guidelines worldwide.

Chemotherapy’s Side-Effects and the Need for Alternatives

Treatment for breast cancer. The world’s most prevalent form of the disease, typically involves surgery to remove tumours, followed by chemotherapy when doctors believe there is a risk the disease will return. However, chemotherapy comes with toxic side-effects, including hair loss, rashes, nausea, insomnia, and fatigue, which are physically and emotionally gruelling for patients — some may face life-changing consequences such as infertility, cognitive impairment, or early menopause.

For decades, there has been little choice for patients. Now scientists have developed a genomic test that can determine who needs chemotherapy and who can safely skip it, leading to a new era of personalised medicine.

Breakthrough in Genomic Testing

The Optima trial. Led by University College London (UCL). Followed more than 4,000 patients with newly diagnosed breast cancer in the UK, Norway, Sweden, Australia, New Zealand, and Thailand. It found that those with a low score on the genomic test could be treated safely with hormone therapy alone, avoiding the side-effects of chemotherapy.

The Prosigna test, developed by Veracyte, analyses the activity of 50 genes in tumour tissue. It determines the molecular subtype and provides a score indicating the risk of breast cancer returning in the next decade. This helps doctors decide whether chemotherapy is necessary.

Results from the trial showed that outcomes were extremely similar whether chemotherapy was given or not. Five years after treatment, 95% of those who had chemotherapy and hormone therapy were alive and free from breast cancer recurrence, while 94% of those who skipped chemotherapy were also alive and recurrence-free. This suggests that for those with low test scores, chemotherapy offered little or no additional benefit.

One participant in the trial told the Guardian that being able to skip chemotherapy felt “like Christmas.” Nine years after her diagnosis, she is healthy and enjoying a full and active life.

Implications for Patients and Healthcare Systems

Prof Rob Stein, the trial’s chief investigator and a professor of breast oncology at UCL, said the test addresses a longstanding challenge in breast cancer care: identifying who truly benefits from chemotherapy. He noted that the trial has successfully used tumour biology to guide decisions rather than relying solely on traditional clinical features.

“For patients, this means many may be spared the physical and emotional burden of chemotherapy and its potential long-term side-effects. For health systems, it represents a more efficient and evidence-based use of resources,” Stein said.

The trial involved 4,429 patients aged 40 or above with hormone-positive breast cancer, which accounts for up to 80% of breast cancer cases globally. Participants were assigned to one of two treatment groups: one receiving standard treatment with chemotherapy followed by hormone therapy, and the other having their tumours analysed with the genomic test.

Those with high scores received chemotherapy and hormone therapy, while those with low scores were treated with hormone therapy alone. Radiotherapy and other treatments were given as usual to both groups.

Professor Iain MacPherson, a co-chief investigator and professor of breast oncology at the University of Glasgow, said the findings represent a major step forward in delivering more personalised care. “Optima provides effective, practice-changing evidence that we can safely reduce the use of chemotherapy for many patients with hormone-sensitive breast cancer,” he said.

Professor David Miles, a leading cancer specialist, described the findings as “practice-changing.” “We can now confidently predict many patients will get no benefit at all, and therefore there’s no need for them to have the chemotherapy,” he told BBC’s Newshour.

UCL noted that more than 5,000 NHS patients a year could avoid chemotherapy as a result of the trial. Karen Bonham, a participant from Cardiff, said the results are an “immense relief.” She avoided chemotherapy thanks to the Prosigna test and has instead received radiotherapy and hormone therapy over the past eight years.