Gene Test Identifies Two-Thirds of Breast Cancer Patients Who Can Avoid Chemotherapy

Millions of breast cancer patients could safely avoid chemotherapy, an international study led by University College London (UCL) has suggested. The research indicates a DNA test can accurately distinguish between patients who will benefit from chemotherapy and those who will not, potentially sparing a significant number from its debilitating side effects.

The study found that more than two-thirds of its participants could be treated effectively with hormone therapy alone, circumventing the fatigue, nausea, hair loss, weakened immune system, and fertility issues associated with chemotherapy.

Involving over 4,000 newly diagnosed patients aged over 40 across the UK, Norway, Sweden, Australia, New Zealand, and Thailand, the study utilised the Prosigna gene test. This test measures the activity of 50 genes linked to breast cancer growth, calculating a patient's risk of recurrence.

Patients who received a low score on the Prosigna test, comprising two-thirds of the cohort, did not undergo chemotherapy. Their five-year survival rate was 93.7%, closely comparable to the 94.9% rate observed in patients who received chemotherapy as part of their treatment. This outcome suggests minimal additional benefit from chemotherapy for this low-risk group.

Typically, after surgical tumour removal, chemotherapy is often recommended to reduce the risk of cancer returning, particularly for early-stage breast cancer that has spread to nearby lymph nodes. Clinicians have long expressed concern that chemotherapy offers limited benefit for the most common types of breast cancer.

UCL projects that this trial's findings could enable over 5,000 NHS patients annually to avoid chemotherapy. Professor Rob Stein, chief investigator and Professor of Breast Oncology at the UCL Cancer Institute, stated, "These results mark an important and significant step toward more personalised treatment." He added that the trial successfully used "tumour biology to guide decisions rather than relying solely on traditional clinical features."

The findings are scheduled for presentation at the American Society of Clinical Oncology's annual meeting in Chicago, United States. However, UCL notes that it will be several years before it is known whether these findings apply to individuals under 40.