Millions of people with hormone-sensitive breast cancer may be able to avoid chemotherapy without reducing their chances of remaining cancer-free, according to findings from a major international clinical trial presented at the American Society of Clinical Oncology (ASCO) annual meeting.
Researchers behind the Optima trial found that a genomic test called Prosigna can identify patients who are unlikely to benefit from chemotherapy after surgery. For many of these patients, hormone therapy alone produced similar outcomes.
The findings could help doctors personalize treatment decisions and reduce unnecessary exposure to chemotherapy and its side effects.
How the Study Was Conducted
The Optima trial enrolled 4,429 patients aged 40 and older with hormone receptor-positive breast cancer. This is the most common type of breast cancer worldwide.
Doctors typically recommend chemotherapy for patients in this group because they face a higher risk of recurrence. Researchers from institutions including University College London and the University of Glasgow used genomic testing to determine whether some patients could safely avoid the treatment.
The study focused on the Prosigna test, which examines the activity of 50 genes within a tumor. The test estimates the likelihood that cancer will return within 10 years and helps identify patients who may benefit most from chemotherapy.
Similar Outcomes Without Chemotherapy
Researchers reported that patients classified as lower risk achieved similar results whether they received chemotherapy or not.
Five years after treatment, 93.7% of patients who received hormone therapy without chemotherapy remained alive and free from breast cancer recurrence. Among those who underwent both chemotherapy and hormone therapy, the figure was 94.9%.
The researchers concluded that omitting chemotherapy did not significantly worsen outcomes for patients identified as lower risk through genomic testing.
Reducing Treatment Burden
Chemotherapy remains an important treatment for many breast cancer patients. However, it can cause significant side effects, including fatigue, nausea, hair loss, fertility complications and cognitive difficulties.
As a result, researchers have increasingly explored ways to identify patients who can safely avoid the treatment.
The Optima investigators estimated that more than two-thirds of patients in the study could potentially skip chemotherapy when doctors used genomic testing to guide treatment decisions.
The findings support the growing use of precision oncology, an approach that tailors treatment based on the biological characteristics of an individual’s tumor rather than relying solely on traditional risk factors.
Part of a Broader Shift in Breast Cancer Care
The results add to a growing body of evidence supporting genomic testing in breast cancer treatment.
Earlier studies involving genomic tools such as Oncotype DX also found that many patients with hormone receptor-positive, HER2-negative breast cancer can safely forgo chemotherapy when genetic testing indicates a low likelihood of benefit.
However, treatment recommendations still depend on several factors, including age, menopausal status, lymph node involvement and specific tumor characteristics.
Researchers stressed that the Prosigna test is not intended to replace chemotherapy altogether. Instead, it helps identify patients who are less likely to benefit from the treatment.
Potential Impact on Future Care
The Optima trial could influence future breast cancer treatment guidelines and help reduce unnecessary chemotherapy use.
Beyond improving patient quality of life, a more targeted treatment approach could lower healthcare costs by avoiding therapies that provide limited benefit.
Researchers said they will continue monitoring trial participants to assess long-term outcomes and confirm the durability of the findings.
The results highlight the increasing role of genomic medicine in cancer care and suggest that many patients may be able to receive effective treatment with fewer side effects.
