A major international clinical trial has found that many breast cancer patients may be able to
safely avoid chemotherapy without increasing their risk of cancer returning. The findings, presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, could significantly change how certain types of breast cancer are treated and help reduce unnecessary exposure to the side effects associated with chemotherapy.
The study, known as OPTIMA (Optimal Personalised Treatment of Early Breast Cancer Using Multi-Parameter Analysis), involved more than 4,400 patients from several countries, including the United Kingdom, Australia, New Zealand, Norway, Sweden, and Thailand. Researchers aimed to determine whether genomic testing could help identify which patients would genuinely benefit from chemotherapy and which could safely receive alternative treatments.
Chemotherapy has long been a standard treatment for many patients diagnosed with early-stage breast cancer, particularly when the disease has spread to nearby lymph nodes. While the treatment can reduce the likelihood of cancer recurrence, it is also associated with a range of side effects, including fatigue, nausea, hair loss, nerve damage, fertility issues, and long-term cognitive effects. As a result, doctors have increasingly sought ways to personalize treatment and avoid unnecessary chemotherapy when possible.
The OPTIMA trial focused on patients with hormone-sensitive, HER2-negative breast cancer, which is among the most common forms of the disease. Researchers used a genomic test called Prosigna, developed to analyze the activity of 50 genes within a tumor. The test helps determine how likely a cancer is to return and whether chemotherapy is likely to provide meaningful benefit.
Using the results of the genomic test, researchers divided patients according to their risk of recurrence. Those identified as having a low genomic risk were either treated with hormone therapy alone or received both hormone therapy and chemotherapy. The outcomes of the two groups were then compared over several years.
The results showed very little difference between the two treatment approaches. Patients who avoided chemotherapy had a five-year cancer-free survival rate of approximately 93.7%, while those who received chemotherapy achieved a rate of about 94.9%. Researchers concluded that chemotherapy provided minimal additional benefit for many patients classified as low risk by the genomic test.
According to the research team, approximately two-thirds of the patients involved in the study fell into the low-risk category. This suggests that a substantial number of future breast cancer patients could potentially avoid chemotherapy if genomic testing confirms that they are unlikely to benefit from it.
Experts say the findings represent an important step toward more personalized cancer treatment. Instead of making treatment decisions based solely on traditional factors such as tumor size and lymph node involvement, doctors can increasingly use genetic information from tumors to guide therapy choices. This approach may help ensure that patients receive treatments tailored to the biological characteristics of their cancer.
Researchers have emphasized that the findings do not mean chemotherapy is no longer necessary for breast cancer treatment. Many patients with higher-risk tumors or different cancer subtypes continue to benefit significantly from chemotherapy. The study applies specifically to patients whose cancers demonstrate low-risk genomic profiles according to the testing criteria used in the trial.
The trial’s results are expected to contribute to ongoing discussions about treatment guidelines and may encourage wider use of genomic testing in breast cancer care. If adopted broadly, this approach could help reduce the physical, emotional, and financial burden associated with chemotherapy while maintaining effective cancer outcomes for suitable patients.
As cancer treatment continues to move toward precision medicine, studies such as OPTIMA highlight how advances in genetic testing are helping doctors make more informed decisions. For many patients diagnosed with hormone-sensitive breast cancer, the ability to avoid chemotherapy without compromising their chances of recovery could represent a significant improvement in quality of life during and after treatment.
