A Genomic Test May Help Some Women With Breast Cancer Avoid Chemotherapy

A breast cancer diagnosis can bring a flood of difficult decisions. After surgery, some women are advised to undergo chemotherapy to reduce the risk of cancer returning. Others may benefit from hormone therapy, radiation, or a combination of treatments.

But does every woman with early-stage breast cancer need chemotherapy?

New findings from the international OPTIMA trial suggest that, for some patients, the answer may be no. Researchers found that a genomic test called Prosigna may help identify women who can avoid chemotherapy without significantly compromising their five-year outcomes. The findings, reported by researchers at University College London in May 2026, could help make breast cancer treatment more targeted.

The important point is that avoiding chemotherapy is not suitable for everyone. The goal is to identify who is most likely to benefit from it—and who may do well without it.

Why Chemotherapy Is Not Always Necessary

Chemotherapy uses medicines to destroy cancer cells or stop them from growing. It can be an essential part of breast cancer treatment, but it can also cause side effects, including fatigue, nausea, hair loss, an increased risk of infection, and nerve problems.

For some patients, these effects are temporary. Others may experience longer-lasting complications.

Breast cancer, however, is not one single disease. Tumors differ in their biology, growth patterns, and likelihood of returning. Two women with similar-looking tumors may have different risks and respond differently to treatment.

Doctors traditionally consider factors such as tumor size, cancer grade, lymph node involvement, and hormone receptor status when recommending chemotherapy. These details remain important, but they may not tell the whole story.

That is where genomic testing can help.

What Does the Prosigna Test Do?

The Prosigna test examines the activity of genes in a sample of breast tumor tissue removed during surgery. It uses this information, alongside factors such as tumor size, to estimate the likelihood of cancer returning.

The test can help classify certain hormone receptor-positive, HER2-negative breast cancers according to their biological characteristics and estimated recurrence risk.

In simple terms, it gives doctors another piece of information beyond what they can see under a microscope.

A lower score may suggest that the cancer has a lower risk of recurrence and that chemotherapy could offer limited additional benefit. A higher score may indicate a greater risk and support recommending more intensive treatment.

However, a genomic score is not a guarantee. Doctors must interpret it alongside a patient’s age, menopausal status, lymph node findings, overall health, and treatment preferences.

What Did the OPTIMA Trial Find?

The OPTIMA trial enrolled 4,429 people with early breast cancer across several countries. It investigated whether using genomic test results to guide treatment could reduce unnecessary chemotherapy.

According to the published summary from UCL, more than two-thirds of participants had a low Prosigna score. Among this group, five-year outcomes were similar between those who received chemotherapy alongside hormone therapy and those who received hormone therapy alone.

The reported results were:

• 94.8% of patients receiving chemotherapy plus hormone therapy were alive and free from breast cancer recurrence at five years.
• 93.6% of patients receiving hormone therapy alone reached the same outcome.

The difference was 1.2 percentage points. Researchers reported that the results fell within the trial’s predefined margin for an acceptable difference.

These findings are encouraging because they suggest that some women may avoid chemotherapy without a meaningful loss in short-term outcomes.

Still, five-year results do not settle every question about long-term recurrence. Breast cancer can return many years after initial treatment, so continued follow-up is important. The findings also apply to the group studied, not automatically to every person with breast cancer.

Who Might Benefit From Genomic Testing?

Genomic tests are most useful for certain types of early-stage breast cancer, particularly hormone receptor-positive, HER2-negative disease. Whether a test can guide treatment depends on the specific assay and the patient’s clinical circumstances.

Menopausal status matters, too. Research from other trials has shown that some premenopausal women with cancer in nearby lymph nodes may still benefit from chemotherapy, even when genomic results suggest a lower risk.

Genomic testing is not a universal reason to avoid chemotherapy, and it is not generally used to make the same treatment decisions for triple-negative or HER2-positive breast cancers.

A specialist can explain whether Prosigna or another validated genomic assay is appropriate for an individual case.

Questions to Ask Your Oncology Team

If you or someone close to you has been diagnosed with breast cancer, consider asking:

• What type of breast cancer do I have, and what are my hormone receptor and HER2 results?
• Would a genomic test help clarify my likely benefit from chemotherapy?
• How do my age, menopausal status, tumor features, and lymph node results affect the recommendation?
• What are the potential benefits and side effects of each treatment option?
• If chemotherapy is not recommended, what other treatments and follow-up care will I need?

These conversations can help turn a frightening decision into a more informed, shared plan.

A More Individual Approach to Cancer Care

The OPTIMA findings reflect an important shift in breast cancer treatment: care is increasingly guided by the biology of an individual tumor, not just its size or location.

For some women, genomic testing may help avoid chemotherapy and its side effects. For others, chemotherapy remains an important part of reducing the risk of recurrence.

The best treatment is not necessarily the most intensive one. It is the treatment plan that offers the most appropriate balance of benefit, risk, and quality of life for the individual patient.

Genomic testing can help inform that decision—but it should always be interpreted by an oncology team, never used on its own to start, stop, or refuse treatment.

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