The purpose of this study is to see whether a specialised laboratory test (Prosigna (PAM50) Assay) of breast cancer tissue can be used to choose women with early ER-positive HER2-negative breast cancer who can safely avoid chemotherapy because there is a low risk of the cancer coming back. New Zealand sites will be Waikato Hospital (lead site), Tauranga Hospital, Wellington Hospital and Palmerston North Hospital.

People with ER-positive, HER2-negative breast cancer are usually offered both chemotherapy and hormone (endocrine) treatment to reduce the risk of the cancer coming back in the breast or elsewhere. Currently we don’t have a single test that can tell us whether or not someone might benefit from chemotherapy, so some people may receive chemotherapy who don’t need it. Chemotherapy can have unpleasant short- and long-term side-effects.

There is some evidence to suggest that the Prosigna test is effective at predicting if patients with breast cancer which has spread to lymph nodes or with larger cancers are likely to benefit from chemotherapy. The OPTIMA trial should provide better evidence for the value of the Prosigna test in deciding on the best treatments for those with early breast cancer.

For more information, click here and here.

29 April 2024

Update 2026:

The first results from this trial were presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in May. 

4,429 people participated – 2,215 were assigned to the control arm (given chemo and endocrine therapy regardless of their Prosigna score) and 2,214 to the test-directed treatment arm (given only endocrine therapy, provided their Prosigna score was < 60).

The 5-year invasive breast cancer free survival rates (i.e. people who were still alive with no recurrence) were 91.5% for the control group and 90.4% for the test-directed group (i.e. no statistically significant difference), showing that the test-directed treatment regime was not inferior to the standard regime.

68% of the participants (across all groups) had low Prosigna scores (< 60). When only the results from these people were considered, the 5-year invasive breast cancer free survival rates were 94.9% for the control group and 93.7% for the test-directed group (not statistically different). This shows that,  for those with low Prosigna scores, there is no benefit derived from receiving chemotherapy as well as endocrine therapy.

The researchers concluded that “The OPTIMA trial demonstrates that women and men with ER positive HER2 negative early breast cancer and ROR (Prosigna) score < 60 tumours can safely avoid chemotherapy.”

18 June 2026