DNA Shed by Tumors Show Promise for Non-Invasive Screening and Prognosis

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Newswise Certain fragments of DNA shed by tumors into the bloodstream can potentially be used to non-invasively screen for early-stage cancers, monitor responses to treatment and help explain why some cancers are resistant to therapies, according to results of an international study led by Johns Hopkins Kimmel Cancer Center investigators.

Analyzing blood samples from 640 patients with various cancers, the researchers used digital polymerase chain reaction-based technology (a sophisticated method of multiplying and measuring the number DNA molecules) to evaluate how well the DNA fragments predicted the presence of tumors in the patients.

The fragments, known as cell-free circulating tumor DNA (ctDNA), were detected in the blood of more than 75 percent of patients with advanced cancers and in at least half of patients with localized, smaller tumors that had not spread outside of the organ where the cancer originated and still had the potential for cure.

Investigators say the work, published Feb. 19 in the journal Science Translational Medicine, provides strong evidence that ctDNA could be used as a personalized biomarker test and cancer screening tool.

Were already very good at treating and curing cancer when it is localized, says lead study author Chetan Bettegowda, M.D., Ph.D., an assistant professor of oncology and neurological surgery. But we wanted to develop a non-invasive technology to enhance detection of cancer at an early stage, and we feel this is an exciting starting point for further work using this method.

The most promising aspect is that ctDNA can identify early-stage cancers, adds one of the studys senior authors, Luis Diaz, M.D., associate professor of oncology and director of the Swim Across America Laboratory at Johns Hopkins.

Among study participants with metastatic cancers, researchers detected ctDNA in 82 percent of patients with solid tumors outside the brain (112 of 136 patients), including more than 75 percent of patients with advanced ovarian, colorectal, bladder, gastroesophageal, pancreatic, breast, hepatocellular, and head and neck cancers, as well as melanomas. Less than 50 percent of patients with medulloblastomas or metastatic cancers of the kidney, prostate or thyroid, and less than 10 percent of patients with gliomas, had detectable ctDNA.

Among 223 patients with localized tumors, researchers detected ctDNA in 55 percent of all patient samples, and in 73 percent of those with colorectal cancer, 57 percent of those with gastroesophageal cancer, 48 percent of those with pancreatic cancer and 50 percent of those with breast adenocarcinoma. Increasing levels of ctDNA correlated with the stage of cancer: 47 percent of patients with Stage I cancers of any type had detectable ctDNA, as did 55 percent of patients with Stage II cancers, 69 percent of patients with Stage III cancers, and 82 percent of patients with Stage IV cancers.

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DNA Shed by Tumors Show Promise for Non-Invasive Screening and Prognosis