Experimental Blood Test Detects Cancer Up To Four Years Before Symptoms Appear

Posted by Sama in Science and Technology On 31st July 2020
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#1

For years scientists have been working on new research to beat cancer. Cancer, that is in a word itself a painful reminder for those who have lost their loved ones to this disease or those who are fighting off this disease.

A piece of good news for all these people. A new method reported today in Nature Communications brings researchers a step closer to the goal where it will be possible to detect cancer earlier and where treatments will be possibly more effective.

“What we showed is: up to four years before these people walk into the hospital, there are already signatures in their blood that show they have cancer,” says Kun Zhang, a bioengineer at the University of California, San Diego, and a co-author of the study. “That’s never been done before.”

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#2

Before this, the diagnosis for cancer included detecting it unfortunately after its spread. This results not only in delayed diagnosis but also too late for any treatment to be effective too.

Past efforts to develop blood tests for cancer typically involved researchers collecting blood samples from people already diagnosed with the disease. They would then see if they could accurately detect malignant cells in those samples, usually by looking at genetic mutations, DNA methylation (chemical alterations to DNA) or specific blood proteins. “The best you can prove is whether your method is as good at detecting cancer as existing methods,” Zhang says. “You can never prove it’s better.”

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#3

In contrast to this, Zhang and his colleagues started collecting samples from people before they had cancer. In 2007 the researchers began recruiting more than 123,000 healthy individuals in Taizhou, China, to undergo annual health checks—an effort that required building a specialized warehouse to store the more than 1.6 million samples they eventually accrued. Around 1,000 participants developed cancer over the next 10 years.

The focus of thee scientists was to develop a test for the five most common cancers that included stomach, esophageal, colorectal, lung, and liver malignancies. The test they developed, called PanSeer, detects methylation patterns in which a chemical group is added to DNA to alter genetic activity. Past studies have shown that abnormal methylation can signal various types of cancer, including pancreatic and colon cancer.

This PanSeer test works by isolating DNA from the blood sample and then measuring DNA methylation at over 500 locations that have the best chances of detecting cancer. A machine-learning algorithm compiles the findings into a single score that indicates a person’s likelihood of having the disease.

The researchers then tested blood samples from 191 participants who eventually developed cancer, paired with the same number of matching healthy individuals. They were able to detect cancer up to four years before symptoms appeared with roughly 90 percent accuracy and a 5 percent false-positive rate.

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#4

The new study “offers several interesting approaches in the quest for a blood-plasma-based cancer-screening test,” says Colin Pritchard, a molecular pathologist at the University of Washington School of Medicine, who was not involved in the research. It will be important, though, for another research team to independently validate the findings in a different group of people before the test can be considered for clinical use, he says.

Usha Menon, a professor of gynecological cancer at University College London, who also did not participate in the study, observes that Zhang and his colleagues’ method provides a robust, preliminary baseline test—an “essential first step” toward a commercial cancer-screening product. “The authors are not suggesting that they have a test that can be used clinically at this stage,” she says. “They are clear that what they have is a robust preliminary demonstration of early detection of multiple cancer types four years prior to conventional diagnosis.”

Menon says this test most probably would first target high-risk populations. The test would also require devising a second panel of tests to enable clinicians to determine the specific cancer type and rule out false positives.

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#5

Zhang believes such a feature could be developed with more work, and he agrees that further studies are needed. Given the challenges in repeating an effort of this magnitude, a government-industry partnership, he says, would ideally undertake the follow-up research. An ideal test would target the most common cancers, as Zhang’s study did, as well as the deadliest ones. “There are cancers where early detection can make a really big difference,” he says. Pancreatic cancer, for example, is the next target Zhang and his colleagues are working on.

Pritchard warns that whenever this test will be available it is to keep in mind that it won't be able to detect all cancers before they become symptomatic. “One cancer might have a very long lead time, where another is very short,” he says. “Cancers that grow very quickly might not be detected even if someone is, for example, doing an annual screening.” It’s possible, too, that some types of malignancies may never be detected by blood tests because they do not produce a measurable signal in blood plasma.

“We are still a ways away from having an accurate blood-based ‘pan-cancer’ screening test. But it is not impossible to achieve,” Pritchard says. “There are several large efforts underway, with some promise for the future.”

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