Chemotherapy has been a standard part of breast cancer treatment for decades. It has helped countless patients survive the disease, but it is also one of the most feared cancer treatments.
Many people experience side effects that can affect daily life for months or even years. Because of this, doctors have been searching for ways to identify which patients truly need chemotherapy and which patients may safely avoid it.
A major international study may have found part of the answer. Researchers led by University College London have shown that a genetic test called Prosigna can help identify many breast cancer patients who can skip chemotherapy without increasing the risk of their cancer returning.
The study, known as the OPTIMA trial, followed 4,429 patients from six countries. It focused on people aged 40 years and older with hormone-sensitive breast cancer.
This is the most common type of breast cancer and is often treated using hormone-blocking medicines. Many participants also had cancer that had spread to nearby lymph nodes, which usually places them in a higher-risk category.
Traditionally, doctors have relied on factors such as tumor size, lymph node involvement, and patient age when deciding whether chemotherapy is needed. While these factors remain important, they do not always accurately predict who will benefit most from treatment.
The Prosigna test takes a different approach. Instead of focusing mainly on what the tumor looks like under a microscope, it examines gene activity within the cancer. This provides information about how aggressive the tumor may be and how likely it is to return after treatment.
In the trial, patients were divided into two groups. One group received standard treatment, which included chemotherapy followed by hormone therapy.
The other group received treatment recommendations based on their Prosigna scores. Patients with higher scores received chemotherapy, while those with lower scores were treated using hormone therapy alone.
Researchers carefully followed participants for five years. The results showed that more than 68 percent of patients had low Prosigna scores. These patients did extremely well whether they received chemotherapy or not.
Among low-score patients who received chemotherapy, 94.8 percent were alive without cancer recurrence after five years.
Among those who did not receive chemotherapy, 93.6 percent remained cancer-free and alive. The difference was so small that researchers concluded chemotherapy provided little or no meaningful benefit for most patients in this low-risk group.
The findings could dramatically change how breast cancer is treated. Every year, thousands of patients endure chemotherapy because doctors cannot be completely certain whether it will help them. This study suggests that genetic testing can provide much clearer answers.
Avoiding chemotherapy can offer significant benefits. Patients may avoid hair loss, fatigue, infections, nerve damage, nausea, and other side effects. Many can return to work, family responsibilities, and normal activities more quickly. Healthcare systems may also save substantial resources by reducing treatments that are unlikely to provide benefit.
One of the strengths of the study is that it included a broad range of patients. Researchers examined both premenopausal and postmenopausal women, as well as patients with different levels of lymph node involvement. The results remained consistent across these groups.
The story of participant Karen Bonham illustrates the potential impact. After her diagnosis in 2017, she expected to undergo chemotherapy. However, the Prosigna test showed she could safely avoid it. Nearly a decade later, she remains well and credits the trial with helping her receive more personalized treatment.
Although the findings are highly promising, the researchers caution that not every breast cancer patient can avoid chemotherapy. Patients with high Prosigna scores still benefited from receiving chemotherapy, and the study does not yet provide clear answers for people under age 40. Additional research is ongoing.
The findings were presented at the 2026 American Society of Clinical Oncology meeting and are expected to influence future treatment guidelines. If widely adopted, the test could help transform breast cancer care by making treatment more personalized and reducing unnecessary exposure to chemotherapy.
Study analysis: This study is important because it moves cancer treatment away from a one-size-fits-all model and toward precision medicine. The large sample size, international design, and randomized approach make the evidence highly reliable.
While additional follow-up is needed, the results strongly suggest that many patients with hormone-sensitive breast cancer can safely avoid chemotherapy when guided by Prosigna testing, improving quality of life without compromising survival.
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Source: University College London (UCL).
