Scientists have developed a blood test that can help predict how patients with breast cancer will respond to treatment, potentially allowing doctors to choose the most effective therapy earlier.
The test analyses circulating tumour DNA (ctDNA), tiny fragments of cancer DNA released into the bloodstream by tumour cells. In a study of 167 people with advanced breast cancer, researchers found that patients with low or undetectable levels of ctDNA before treatment, or after just four weeks, were far more likely to respond well to therapy.
Those patients typically experienced longer periods before their cancer progressed and higher rates of tumour shrinkage compared with patients whose ctDNA levels remained high. The findings held true across different breast cancer subtypes, including aggressive forms such as triple-negative breast cancer.
Researchers say the test could help avoid giving patients treatments that are unlikely to work, allowing doctors to switch earlier to alternative drugs or clinical trials. Further trials are under way to confirm whether using the test to guide treatment decisions improves long-term outcomes.
