Genetic test may help identify breast cancer patients who can avoid chemotherapy

Results of a large international trial suggest that a significant share of people with breast cancer may be able to safely forgo chemotherapy, guided by a test that reads the genetic activity of their tumour. More than two-thirds of the patients in the study were treated with hormone therapy alone, a treatment that blocks the hormones some breast cancers need to grow.

How the trial worked

Led by University College London (UCL), the study involved more than 4,000 newly diagnosed patients over the age of 40 in the UK, Norway, Sweden, Australia, New Zealand and Thailand. Researchers used a test called Prosigna, which measures the activity of 50 genes involved in breast cancer growth and uses the result to estimate how likely the disease is to return.

Patients with a low score, around two-thirds of the group, did not receive chemotherapy. Their five-year survival rate was 93.7%, compared with 94.9% among patients who received chemotherapy.

Why it matters

Breast cancer is usually treated first with surgery to remove the tumour, and chemotherapy is often recommended afterwards to reduce the risk of the cancer returning. It is also commonly offered when early-stage cancer has spread to the nearby lymph nodes, the small glands that form part of the body's immune system.

Chemotherapy can cause fatigue, nausea, hair loss, a weakened immune system and fertility problems. According to UCL, clinicians have been concerned that it offers little benefit to patients with the most common type of breast cancer.

Professor David Miles, a leading cancer specialist, described the findings as a change to clinical practice. He noted that doctors have long given chemotherapy to large numbers of women knowing only around one in ten would benefit, and that the test now allows them to identify with confidence a large group who can be spared the treatment and its side effects.

What comes next

The findings were due to be presented at the annual meeting of the American Society of Clinical Oncology in Chicago, the world's largest cancer conference. It is not yet known whether the results apply to patients under 40, and UCL said an answer is still several years away.

Source: BBC, «Millions of breast cancer patients could safely avoid chemotherapy, study suggests», Alicia Curry