New trial results suggest chemotherapy may be unnecessary in certain breast cancer patients.
New research suggests less treatment does not impact survival outcomes in people with hormone-positive breast cancer.
The findings of the Optimal Personalised Treatment of early breast cancer using Multi-parameter Analysis (OPTIMA) trial were presented at the 2026 American Society of Clinical Oncology (ASCO) meeting in the United States last month.
The OPTIMA trial recruited 4429 patients with newly diagnosed breast cancer worldwide, including 264 from Australia and New Zealand, to determine whether it is safe to treat individuals with a low Prosigna test score with hormone blocking therapy alone instead of chemotherapy.
Prosigna is a genomic test that measures the activity of genes known to contribute to the growth of breast cancer. Men and women over the age of 40 who had undergone surgery for hormone-positive breast cancer were randomised to receive either standard treatment (chemotherapy followed by hormone blocking therapy) or test-directed treatment (where people with a Prosigna score above 60 received standard treatment but people with a score of 60 or less only received hormone blocking therapy).
Over two thirds of participants (68%) had a Prosigna score less than or equal to 60. Five-year survival rates were similar among the low-scoring cohort: 8% of people who received both chemotherapy and hormone blocking therapy were alive and free from breast cancer recurrence compared to 6% of patients who only received hormone therapy.
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Similar outcomes were observed when pre- and post-menopausal women were considered separately. The researchers attributed this finding to the fact that all premenopausal women received hormone blocking therapy that included ovarian function suppression, which limited any potential additional benefits of chemotherapy.
Associate Professor Belinda Kiely, a medical oncologist specialising in the treatment of breast cancer, said the OPTIMA trial proved that treatment decisions could be guided by tumour biology instead of traditional clinical features.
“OPTIMA addresses a long-standing challenge in breast cancer care: identifying who benefits from chemotherapy and who does not,” the chair of the Australian arm of the study said in a statement.
“These findings show that chemotherapy offers little or no additional benefit for people with low Prosigna scores, meaning a substantial number of patients could safely avoid it and its physical and emotional side effects without compromising their outcomes. The results mark a significant step toward more personalised treatment.”
