Being able to easily track cancer development and progression is vital in all stages of the disease. Healthcare professionals have long been able to monitor disease by taking small tissue samples (biopsies or cytological specimens), but now a new approach is becoming available to them: the liquid biopsy, which can deliver a lot of detailed information about a patient’s tumour from a simple blood sample.

So how does it work? Inside a tumour, cells are growing at a high rate, but while many cancer cells are growing, some are also dying in a process called apoptosis or necrosis. During this process or with an active mechanism, cancer cells release fragments of their DNA. Some of that DNA can get into the bloodstream, the so-called circulating tumour DNA (or ctDNA). This circulating tumour DNA is ready for scientists to fish out with a simple blood sample.

Because of advances in DNA sequencing technology, healthcare professionals can pick up on these traces of DNA and use them to track the mutations within cancer. Finding out this information may help healthcare professionals to keep track of a patient’s tumour and whether treatment is working, or find out early if a new scan or different treatment is needed.