Scientists have developed a simple blood test that can predict how well patients with breast cancer will respond to specific treatments, potentially allowing doctors to tailor therapy much earlier and improve outcomes.
The test works by analysing circulating tumour DNA (ctDNA) in the blood, which is released by cancer cells. In a study involving 167 patients with advanced breast cancer, researchers measured ctDNA levels before treatment began and again after four weeks. They found a strong link between low or undetectable ctDNA levels and better responses to therapy.
Patients with lower ctDNA levels at the start of treatment were more likely to see their tumours shrink and experienced longer periods before their disease progressed. Similar patterns were seen after four weeks of treatment, with particularly strong results among patients whose ctDNA became undetectable.
The study included patients with different types of breast cancer, including those with specific genetic mutations who received targeted therapies, as well as patients with triple-negative breast cancer, an aggressive form of the disease with limited treatment options. In both groups, ctDNA levels proved to be a useful predictor of how well treatments worked.
Researchers say the test could help doctors avoid giving patients drugs that are unlikely to benefit them and instead switch earlier to alternative treatments or clinical trials. Further trials are now under way to determine whether adjusting treatment based on early ctDNA results leads to better long-term outcomes.
