OPTIMA Trial Finds a Gene-Expression Test Can Spare Two-Thirds of High-Risk Breast Cancer Patients From Chemotherapy
The 4,429-patient Phase III OPTIMA trial found that a Prosigna ROR-guided strategy was non-inferior to standard chemotherapy in ER-positive, HER2-negative early breast cancer, letting 68% of clinically high-risk patients skip chemo.
Overview
A gene-expression test can identify clinically high-risk early breast cancer patients who can safely forgo chemotherapy without compromising five-year outcomes, according to results from the Phase III OPTIMA trial presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting as Abstract 500, as reported by The ASCO Post. The trial randomly assigned 4,429 patients and found that a strategy guided by the Prosigna Risk of Recurrence (ROR) score was non-inferior to standard chemotherapy followed by endocrine therapy, allowing roughly two-thirds of participants to avoid chemotherapy entirely.
What We Know
OPTIMA enrolled women and men aged 40 years or above with estrogen receptor-positive, HER2-negative early breast cancer and 0 to 9 involved axillary nodes, according to The ASCO Post. Node-negative patients additionally needed a tumor of at least 30 mm. All participants had clinical features that would conventionally make them candidates for chemotherapy.
The 4,429 patients were split into a control arm and a test-directed arm of 2,214 patients, per The ASCO Post. In the test-directed arm, tumors were profiled with the Prosigna gene-expression test, which produces an ROR score: patients scoring above 60 received chemotherapy plus endocrine therapy, while those scoring 60 or below received endocrine therapy alone. In the control arm, patients received standard chemotherapy followed by endocrine therapy regardless of their genomic profile.
The central finding is that 68% of patients in the test-directed arm had low ROR scores and avoided chemotherapy, according to The ASCO Post. OncoDaily likewise reported that 68% of test-directed patients had low-ROR-score tumors.
The primary endpoint was five-year invasive breast cancer-free survival (IBCFS). In the per-protocol population, OncoDaily reported a five-year IBCFS rate of 91.8% in the control arm versus 90.3% in the test-directed arm, with an adjusted hazard ratio of 1.03 (90% CI, 0.85-1.25) and a non-inferiority p-value of 0.006 — meeting the trial’s predefined non-inferiority margin. The ASCO Post reported the result with a hazard ratio of 0.99 (90% CI, 0.81-1.20) and a non-inferiority p-value of 0.013, over a median follow-up of 3.9 years.
Among the subgroup of patients with low ROR scores, the five-year IBCFS rate was 94.8% in the control arm and 93.6% in the test-directed arm, according to OncoDaily — a small absolute difference that the investigators interpret as evidence the omitted chemotherapy contributed little benefit in this genomically defined group.
The trial was led by chief investigators Rob Stein, Professor of Breast Oncology at the UCL Cancer Institute in London, and Iain MacPherson, Professor of Breast Oncology at the University of Glasgow, and was funded by University College London, the National Institute for Health and Care Research, and Veracyte Inc., according to The ASCO Post.
Stein framed the result as addressing a persistent clinical dilemma. “OPTIMA addresses a long-standing challenge in breast cancer care: identifying who truly benefits from chemotherapy and who does not,” he said, adding that “these results mark an important and significant step toward more personalized treatment,” according to The ASCO Post. MacPherson said the trial “provides robust, practice‑changing evidence that we can safely reduce the use of chemotherapy for many patients with hormone‑sensitive breast cancer,” per the same report.
Why It Matters
Genomic tests have historically been used mainly to confirm that lower-risk breast cancer patients can skip chemotherapy. OPTIMA extends that logic into a population traditionally considered higher risk because of nodal involvement or larger tumors — the patients who would otherwise be steered toward chemotherapy by default.
Ahead of the meeting, breast medical oncologist MinhTri Nguyen of The Ohio State University Comprehensive Cancer Center, quoted in a CancerNetwork preview, said that if OPTIMA were positive and clinicians could use genomic testing to guide chemotherapy decisions, the result could be practice-changing. The trial’s reported non-inferiority across both the full per-protocol analysis and the low-ROR subgroup is consistent with that expectation.
What We Don’t Know
The data reported so far come from the ASCO presentation; a peer-reviewed journal publication was not available at the time of reporting, and longer-term follow-up beyond the roughly four-year median will be needed to confirm that survival outcomes remain equivalent. The reported five-year IBCFS figures and statistics differ slightly between outlets — reflecting different analysis populations and cuts — so the precise endpoint values should be read against the eventual full publication. How quickly ROR-guided de-escalation is adopted into routine practice, and how payers and guideline bodies respond, also remains to be seen.