A new blood test, known as a liquid biopsy, may be capable of detecting the return of cancer months before it becomes visible on conventional imaging scans, according to researchers. This test identifies minute fragments of circulating tumor DNA (ctDNA) in the bloodstream, looking for genetic alterations associated with cancer.
Researchers reviewed extensive evidence from numerous studies and clinical trials on ctDNA. Their findings suggest that ctDNA can indicate whether a treatment is effective, identify mutations that can guide subsequent medical decisions, and detect minimal amounts of residual cancer in the body. An early increase in ctDNA levels could potentially enable physicians to modify treatment strategies before tumor progression is observable through standard imaging techniques.
In one trial involving 130 individuals with bowel cancer, ctDNA detected signs of recurrence approximately nine months prior to detection by conventional imaging. The test also holds the potential to help certain patients forgo unnecessary chemotherapy. A separate bowel cancer trial indicated that patients whose treatment was guided by ctDNA experienced outcomes comparable to those receiving standard care, with a reduced need for chemotherapy.
However, researchers emphasized that ctDNA testing is not infallible. Some cancers release very little DNA into the bloodstream, which could lead to missed detections. Furthermore, the optimal clinical response when ctDNA indicates cancer presence but scans show no disease remains unclear. The review, published in the medical journal JAMA, noted that while ctDNA may aid in selecting optimal treatments and their timing, its definitive clinical applications are still being determined. The researchers also cautioned that a negative ctDNA test does not definitively confirm the absence of a genetic change within the cancer itself.
Liquid biopsy testing is currently available through the UK's National Health Service (NHS) 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 therapies, with some lung cancer patients receiving treatment decisions about two weeks sooner than typically occurs.