Cambridge

A major international study has found that a genetic test called Prosigna can help identify many women with early-stage breast cancer who may safely avoid chemotherapy, potentially sparing them from significant side effects without substantially affecting their chances of long-term survival.

What is the test?

Unlike traditional assessments that focus on tumour size, appearance and lymph node involvement, the Prosigna test analyzes the activity of specific genes within cancer cells. Based on these genetic patterns, it generates a score indicating how aggressive the tumour is and how likely it is to return after treatment.

• Low score: Cancer is less aggressive; surgery, radiotherapy and hormone therapy may be sufficient.
• High score: Greater risk of recurrence; chemotherapy is more likely to provide meaningful benefit.

Why is the finding important?

The results come from the Optima trial, led by researchers at University College London, involving more than 4,400 patients aged 40 and above with hormone receptor-positive, HER2-negative early breast cancer—the most common subtype of the disease.

The study found that more than two-thirds of women who would traditionally be considered for chemotherapy could potentially avoid it if they had a low Prosigna score, without significantly increasing the risk of cancer recurrence.

This could spare many patients from chemotherapy-related side effects such as:

• Hair loss
• Nausea and fatigue
• Increased infection risk
• Early menopause
• Fertility issues
• Long-term heart and nerve damage

Survival outcomes

Researchers reported a small difference in five-year survival rates:

• 94.9% among patients who received chemotherapy
• 93.7% among those who avoided chemotherapy based on genetic testing

The approximately one-percentage-point difference was considered small enough for researchers to conclude that the gene-guided approach performed comparably to standard treatment strategies for eligible patients.

Who still needs chemotherapy?

About one-third of patients in the study received high-risk scores.

For these individuals, chemotherapy remains important because it significantly lowers the risk of the cancer returning. The test therefore helps doctors direct chemotherapy toward patients most likely to benefit while reducing unnecessary treatment for others.

Does this apply to all breast cancer patients?

No. The findings apply specifically to:

• Patients aged 40 and older
• Early-stage breast cancer
• Hormone receptor-positive disease
• HER2-negative cancer

The results do not directly apply to more aggressive forms such as:

• HER2-positive breast cancer
• Triple-negative breast cancer

Treatment decisions for younger patients and other cancer subtypes remain more individualized.

What happens next?

The Prosigna test is already available in some healthcare settings, but the Optima trial provides stronger evidence supporting its wider use in treatment planning. Health authorities and clinical guideline bodies will review the findings before deciding whether to expand routine access.

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Key takeaway

The study represents an important step toward personalized cancer treatment. Rather than treating all patients with similar-looking tumours the same way, doctors may increasingly use genetic information to determine who truly benefits from chemotherapy and who can safely avoid it, reducing overtreatment while maintaining effective cancer care.