Using a modern DNA sequencing technique, Johns Hopkins researchers have come one step closer to diagnosing early-stage cancer patients with a simple blood draw.
The method reads free circulating DNA in a patient’s blood and detects common cancer mutations. While further refinement is needed, it was able to identify three out of every five people with early-stage colorectal, ovarian, breast or lung cancer.
The study, “Direct detection of early-stage cancers using circulating tumor DNA,” published in the journal Science Translational Medicine, describes the noninvasive approach that may also help doctors in choosing appropriate and timely treatments for these patients.
All cancers begin when one or more genes in a cell mutate, allowing the cell to proliferate excessively and to escape controls intended to kill abnormal cells. Identifying these early genetic changes could help to identify people as cancer starts to spread and the best therapeutic options for each of them.
Previous studies have shown that DNA from tumors cells can be detected in the blood stream. Now, a team of researchers at the Johns Hopkins Kimmel Cancer Center devised a strategy to see if they could detect circulating DNA marking early tumors.
The researchers analyzed blood samples from 44 healthy people and 200 patients with different types of cancer, including ovarian cancer, and at different disease stages.
The technique they used is called targeted “error correction sequencing” and is a method for “deep” DNA sequencing. This approach allows researchers to read a DNA sequence thousands of time, greatly improving its sensitivity and allowing them to detect small DNA alterations.
With this technique, the team scanned the blood samples for mutations in 58 cancer-related genes. While healthy people had no tumor-derived mutations, 77 percent of patients with advanced cancers (stages 3 or 4) and 62 percent of those with stage 1 or 2 cancers had tumor-related DNA mutations.
Team members also investigated whether the amount of tumor DNA in circulation might predict how colorectal cancer patients will fare after surgery. They found high tumor DNA levels predicted poorer survival and a greater likelihood cancer recurrence in the patients.
“This study shows that identifying cancer early using DNA changes in the blood is feasible and that our high accuracy sequencing method is a promising approach to achieve this goal,” the study’s lead author, Victor Velculescu with the Hopkins center, said in a press release.
Overall, the findings “provide a broadly applicable approach for noninvasive detection of early-stage tumors that may be useful for screening and management of patients with cancer,” the study concluded.
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