“This study shows that our blood-based method, Pathlight, which reliably measures small fragments of tumor DNA, can provide early information about how breast cancer responds to chemotherapy before surgery while also indicating whether the disease has come back after surgery,” says Lao Saal, researcher at Lund University and senior author of the study, which is now published in the journal EMBO Molecular Medicine.

Among patients who later developed metastatic disease, the blood test detected signs of recurrence a median of 13.8 months before the relapse became clinically visible, and in some cases nearly four years before current methods detected the disease.