Dr Robert Stein speaks to ecancer about data he presented at ASCO 2026 from the OPTIMA phase III trial.

This trial demonstrated that using the Prosigna (PAM50) gene expression test to guide treatment decisions can safely reduce chemotherapy use in patients with ER-positive, HER2-negative early breast cancer.

In this large randomised study of over 4,400 patients, those with low-risk tumours (ROR ≤60) who received endocrine therapy alone achieved non-inferior 5-year invasive breast cancer free survival compared to standard chemotherapy plus endocrine therapy.

Survival outcomes were consistent across key subgroups, including premenopausal patients and those with node-positive disease.

Dr Stein says that these findings support a personalised, biomarker-driven approach to treatment, allowing many patients to avoid unnecessary chemotherapy without compromising outcomes, and reinforcing the clinical utility of genomic testing in early breast cancer management.