Circulating Tumor DNA in Blood Used to Track Cancer Treatment Outcomes

Two new studies suggest a role for blood tests, or liquid biopsies, in guiding a patient’s cancer treatment. The research, which involved patients with breast and prostate cancers, scanned blood for traces of circulating tumor DNA—an approach that is much less invasive than standard tissue biopsies.

The first study was published November 4 in the journal Nature Communications.1 Over 3 years, researchers compared blood and tissue biopsies from a woman with metastatic breast cancer and found that plasma samples reflected genetic changes in her tumors as the cancer progressed.

“Our results show that circulating tumor DNA provides a dynamic sampling of somatic alterations reflecting the size and activity of distinct tumor sub-clones,” the researchers reported. “Analysis of circulating tumor DNA reflects the clonal hierarchy determined from multiregional tumor sequencing and tracks different treatment responses across metastases.”

Noting that the investigation focused on a single woman, researchers acknowledged that the findings need to be confirmed in a larger group of patients. Still, the results provide proof-of-principal that analyzing circulating tumor DNA can accurately monitor cancer in the body.

“The potential of using plasma DNA for molecular stratification and tracking of resistant clones in patients treated with targeted therapies heralds a new era for precision cancer medicine,” they wrote.

The second study, also published November 4, appeared in Science Translational Medicine.2 Researchers sequenced 274 blood samples from 97 men with prostate cancer. The blood samples were collected before and during treatment with an androgen receptor-targeting drug. 

Upon analysis, researchers discovered that even before initiation of the androgen receptor-targeting treatment, many men who went on to develop resistance harbored mutations in the androgen receptor gene. These men were more likely to respond poorly to the treatment and experience worse survival, the study showed.

“This could suggest that patients with aberrant plasma androgen receptor should be selected for treatments such as chemotherapy or radiopharmaceuicals,” researchers wrote.

They, too, noted their findings should be validated in future clinical trials. “Overall, the association of genomic aberrations with clinically meaningful endpoints in our study suggests that circulating tumor DNA is representative of tumor clones that are driving disease progression in castration-resistant prostate cancer,” they wrote. - Jolynn Tumolo

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1. Murtaza M, Dawson SJ, Pogrebniak K, et al. Multifocal clonal evolution characterized using circulating tumour DNA in a case of metastatic breast cancer. Nat Commun. 2015;6:8760.

2. Romanel A, Tandefelt DG, Conteduca V, et al. Plasma AR and abiraterone-resistant prostate cancer. Sci Translational Med. 2015;7:312re10.