The DNA that is shed into the bloodstream from dying cancer cells might one day be used to monitor the disease.

Carlos Caldas at the Cancer Research UK Cambridge Institute and his colleagues identified genetic markers to track disease in 30 women being treated for advanced breast cancer. They found that a technique to detect these markers in cancer-cell DNA in the blood was more sensitive than tests that look for circulating tumour cells or for a cancer antigen. The amount of tumour DNA also roughly correlated with the response to treatment.

The authors suggest that blood tests based on tumour DNA could be quicker and less-invasive than biopsies.

N. Engl. J. Med. http://dx.doi.org/10.1056/NEJMoa1213261 (2013)