ASCO Perspective

"We continue to see promising reports about possible uses of circulating tumor DNA analysis. While this approach has a ways to go before it becomes a proven technology for early cancer detection, this research is an important step in that direction," said ASCO Expert John Heymach, MD, PhD.

CHICAGO - In a study of 124 patients with advanced breast, lung, and prostate cancers, a new, high-intensity genomic sequencing approach detected circulating tumor DNA at a high rate. In 89% of patients, at least one genetic change detected in the tumor was also detected in the blood. Overall, 627 (73%) genetic changes found in tumor samples were also found in blood samples with this approach.
The study will be featured in a press briefing today and presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting.

This innovative approach - using high-intensity sequencing to detect cancer from circulating tumor DNA in the bloodstream - heralds the development of future tests for early cancer detection.

The high-intensity sequencing approach used in this study has a unique combination of breadth and depth. It scans a very broad area of the genome (508 genes and more than two million base pairs or letters of the genome, i.e. A, T, C, and G) with high accuracy (each region of the genome is sequenced or "read" 60,000 times), yielding about 100 times more data than other sequencing approaches. This enormous amount of data will be instrumental in developing a blood test to detect cancer early.

This approach, however, differs from liquid biopsies, including commercial tests, which only profile a relatively small portion of the genome in patients already diagnosed with cancer for the purpose of helping monitor the disease or detect actionable alterations that can be matched to available drugs or clinical trials.

"Our findings show that high-intensity circulating tumor DNA sequencing is possible and may provide invaluable information for clinical decision-making, potentially without any need for tumor tissue samples," said lead study author Pedram Razavi, MD, PhD, a medical oncologist and instructor in medicine at Memorial Sloan Kettering Cancer Center (MSK) in New York, NY. "This study is also an important step in the process of developing blood tests for early detection of cancer."

Circulating tumor DNA is a term used to describe the tiny pieces of genetic material that dying cancer cells shed into the blood circulation. To create a picture of the entire genomic landscape of the tumor from circulating tumor DNA, scientists "read" each tiny fragment and then piece them together as a puzzle. In the bloodstream, circulating tumor DNA is only a small subset of the total cell-free DNA, as most circulating fragments of genetic material come from normal cells.

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