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Tumor DNA in Circulating Blood: Promising Treatment Marker for Breast Cancer

Among breast cancer patients, the presence of DNA from cancer cells that can be found in circulating blood appears to provide greater accuracy than standard methods for determining responses to treatment. These results were recently published in the New England Journal of Medicine.

Patients with advanced breast cancer are often monitored for responses to treatment. Standard ways in which to determine responses include measurement of whole cancer cells in circulating blood, a “tumor marker” protein referred to as CA 15-3 which can also be found in circulating blood, and scans (computed tomography (CT), x-rays, etc).

Although levels of CA 15-3 and circulating tumor cells can be used to determine responses to therapy, researchers continue to explore ways in which to improve upon the accuracy of these standard tests so that treatment may be modified if necessary. .

More recently, researchers have been evaluating the fragments of DNA from cancer cells that are found in circulating blood and their potential correlation to measuring responses to therapy.

A recent clinical trial further explored the potential of DNA found in circulating blood and its association with treatment responses. The trial included 30 women with advanced breast cancer.

Researchers compared the accuracy in determining responses to treatment between DNA fragments from cancer cells in the blood to standard tests (CA 15-3 and whole cancer cells found in the blood).

Results from all 3 methods were compared against results from scans.

DNA fragments from circulating blood were identified in 97% of women, while CA 15-3 was only detected in 78% of women and cancer cells in circulating blood were detected in only 87% of women.
DNA fragments were associated with the highest accuracy in correctly identifying responses to therapy.
The researchers concluded that “This proof-of-concept analysis showed that circulating tumor DNA is an informative, inherently specific, and highly sensitive biomarker of metastatic breast cancer.” Future trials further evaluating this laboratory method will define its clinical value for patients with breast cancer.

Reference: Dawson S-J, Tsui D, Murtaza M, et al. Analysis of Circulating Tumor DNA to Monitor Metastatic Breast Cancer. New England Journal of Medicine. 2013; 368:1199-1209. DOI: 10.1056/NEJMoa1213261.