Blood Test Could Detect Cancer Recurrence Months Earlier Than Scans, Study Suggests

A novel blood test, known as a liquid biopsy, shows promise in detecting the return of cancer months before it is visible on conventional scans, according to research. The test identifies minute fragments of circulating tumor DNA (ctDNA) in the blood, analyzing them for genetic alterations associated with cancer.

Researchers analyzed data from numerous previous studies and clinical trials focusing on ctDNA. Their findings suggest that ctDNA can indicate treatment effectiveness, identify mutations that guide clinical decisions, and reveal minimal amounts of residual cancer in the body.

An early increase in ctDNA levels could potentially prompt doctors to modify treatment strategies before tumor progression becomes apparent through standard imaging techniques. In one study involving 130 individuals with bowel cancer, ctDNA detected the disease's recurrence approximately nine months prior to its identification via imaging.

This type of testing may also help some patients avoid unnecessary chemotherapy. A bowel cancer trial demonstrated that patients whose treatment was informed by ctDNA experienced comparable outcomes to those receiving standard care, but with a reduced incidence of chemotherapy administration.

However, the researchers emphasized that ctDNA is not infallible. Some cancers shed minimal DNA into the bloodstream, which could lead to the test missing the disease. It remains unclear how clinicians should respond when ctDNA indicates cancer presence but scans show no disease.

"ctDNA may help select the best treatment and timing of therapy for a patient with cancer, but optimal clinical applications remain unclear," the researchers stated in their review, published in the medical journal Jama. They also cautioned that a negative ctDNA test does not definitively rule out the presence of a genetic change within the cancer itself.

Liquid biopsy testing is currently available through the National Health Service (NHS) in the UK for eligible lung cancer patients and for specific genomic testing in breast cancer cases. NHS England reports that this approach can expedite access to targeted treatments, with some lung cancer patients receiving treatment decisions about two weeks sooner than usual.