Genomic Test May Spare More Early Breast Cancer Patients From Chemotherapy

For women diagnosed with early-stage breast cancer, chemotherapy is a standard but grueling treatment. Determining who truly needs it has been an ongoing clinical challenge. The OPTIMA trial, presented at the American Society of Clinical Oncology meeting, offers new evidence that genomic testing can safely guide chemotherapy decisions for a broader group of women than previously supported by data.

Currently, tumor gene expression tests like MammaPrint and Oncotype are used to assess chemotherapy benefit in hormone receptor-positive, HER2-negative early breast cancer. However, strong evidence has been limited to postmenopausal women with up to three positive lymph nodes. Premenopausal women and those with more lymph node involvement have lacked reliable data — until now.

OPTIMA enrolled women aged 40 and older with up to nine positive lymph nodes. Participants were randomized to standard chemotherapy followed by endocrine therapy, or to a test-directed arm using the Prosigna genomic assay. Women classified as low risk by Prosigna received endocrine therapy alone. The trial met its noninferiority threshold: the observed outcome difference was just 1.5%, below the 3% margin set by the trial design.

Notably, premenopausal women in OPTIMA received consistent ovarian function suppression, addressing a key gap from prior trials. This subgroup, along with women carrying higher lymph node burden, showed similar noninferiority results — suggesting the genomic-guided approach holds across these historically underserved populations.

Several caveats temper enthusiasm. Most participants had less than five years of follow-up, meaning long-term recurrence data are incomplete. Women under 40 were excluded, so findings cannot be applied to younger patients. The trial population was also predominantly white, limiting generalizability across ethnicities. Broader clinical adoption will likely await longer follow-up and more diverse replication.