Contributed by Cancer Treatment Centers of America


Tumor DNA provides a specific biomarker allowing cancer to be detected and tracked in patients, however retrieving that DNA using a biopsy is invasive and carries a risk of side effects.

In recent years, scientists have discovered that dying tumor cells release pieces of their DNA into your bloodstream, and this circulating tumor DNA (ctDNA) can be detected via a blood test.

CtDNA can be used to track tumor burden (the number of cancer cells, size of a tumor and the amount of cancer in your body), but new research revealed it may also be useful in tracking cancer as it metastasizes or spreads.

In a case study of a 42-year-old woman diagnosed with invasive ductal carcinoma, the most common type of breast cancer, researchers compared tissue biopsies with a blood test for ctDNA, known as a “liquid biopsy.”

An analysis of the tests showed that ctDNA in blood samples tracked mutations in the woman’s cancer, even as it spread to other parts of her body, including her backbone, chest and liver. CtDNA collected through liquid biopsies also identified the tumor sites that developed resistance to therapy.

While conducting multiple biopsies isn’t typically practical or advisable, liquid biopsy can be conducted much more frequently to provide up-to-date information about the course of the cancer. This information could then help physicians decided on targeted treatments for individual patients at each stage of their disease.

Study author Dr. Murtaza, Co-Director of the Translational Genomics Research Institute’s (TGen) Center for Noninvasive Diagnostics, explained:

“When patients receive therapy for advanced cancers, not all parts of the tumor respond equally, but it has been difficult to study this phenomenon because it is not practical to perform multiple, repeated tissue biopsies … Our findings empirically show that ctDNA analysis from blood samples allows us to detect cancer mutations from multiple different tumor sites within a patient and track how each of them responds.”

Using circulating tumor DNA to track how a patient’s cancer responds to treatment in real-time has been described as a potential “new era for precision medicine.” More studies are needed before such tests will be widely available, but the hope is that they may one day allow for more targeted, personalized cancer treatment.

Nature Communications November 4, 2015
TGen November 4, 2015
National Human Genome Research Institute