A biopsy sample of tissue often is tested for specific genetic variations (also referred to as mutations) that may have a targeted inhibitor that represents a clear optimal treatment for that cancer. However, it may not be possible to get enough tissue from the tumor to do these studies. DNA from our cells, including cancer cells, breaks down as part of its normal life cycle. This causes it to be shed into the bloodstream, where it is known as circulating tumor DNA (ctDNA). It is now possible to look for a wide range of cancer-associated variations in the ctDNA in a patient’s blood sample. Read more.