Cancer detected up to 4 years before symptoms appear on blood test

For years, scientists have sought to create the ultimate cancer screening test. This is a test that can detect malignant tumors early and reliably before the spread of tumor cells and when the treatment is more effective. New method reported today Natural communication Bringing researchers one step closer to that goal. By using a blood test, an international team Diagnose cancer long before symptoms appear in almost everyone tested A person who has developed cancer.

“We have shown that these people already have a signature in their blood that they have cancer, up to four years before they enter the hospital.” Zhang, Is a bioengineer and co-author of research at the University of California, San Diego. “Never done before.”

Past efforts to develop blood tests for cancer have typically included researchers who collect blood samples from people already diagnosed with the disease. Next, we usually check for genetic mutations, DNA methylation (chemical changes to DNA), or certain blood proteins to see if these cells can accurately detect malignant cells. “The best you can prove is whether your method is as good at detecting cancer as the existing methods,” says Zhang. “We can’t prove it better.”

In contrast, Zhang et al. began collecting samples from people before they showed signs of cancer. In 2007, researchers began recruiting more than 123,000 healthy individuals each year in Taizhou, China, and received annual health checks. About 1,000 participants developed cancer over the next 10 years.

Zhang and colleagues focused on developing tests for the five most common types of cancer: malignant tumors of the stomach, esophagus, colorectal, lung, and liver. A test they developed, called PanSeer, detects methylation patterns in which chemical groups are added to DNA to alter genetic activity. Past studies have shown that aberrant methylation can be a sign of various types of cancer, including pancreatic and colon cancers.

The PanSeer test works by isolating DNA from blood samples and measuring DNA methylation at the 500 locations previously identified as being most likely to indicate the presence of cancer. Machine learning algorithms combine survey results into a single score to indicate the likelihood that the person will be ill. The researchers tested blood samples from 191 participants who eventually developed cancer in combination with an equal number of matching healthy individuals. They were able to detect cancer with accuracy of approximately 90% and false positive rate of 5% for up to 4 years before symptoms appeared.

The new study says, “It offers some interesting approaches in the quest for blood plasma-based cancer screening tests.” Colin Pritchard, A molecular pathologist at the University of Washington School of Medicine, who was not involved in the study. But it is important that another research team independently validate the findings of another group before considering its clinical use, he said.

Usha MenonSince he was also a professor of gynecologic cancer at the University of London, but did not participate in this study, Professor Zhang’s method provided a robust preliminary baseline test, making it a “must have” for commercial cancer screening products. It’s the first step.” “The authors do not suggest that they have clinically available tests at this stage,” she says. “It’s clear that what they have is a strong preliminary demonstration of early detection of multiple cancer types four years before conventional diagnosis.”

Most likely, such tests would first target high-risk populations, Menon said. Also, a second panel of tests should be devised to help clinicians identify specific cancer types and rule out false positives.

Zhang believes that such functionality can be developed with more work and agrees that further research is needed. Given the challenges of repeating this scale of effort, He says government-industry partnerships would ideally address follow-up studies. An ideal test would cover the most common and most deadly cancers, as Zhang’s study did. “There are cancers where early detection can make a huge difference,” he says. Pancreatic cancer, for example, is the next target Zhang and his colleagues are working on.

If a blood test for cancer becomes available, Pritchard will warn you, but he may not be able to detect all cancers before they show symptoms. “One cancer may have a very long lead time, while another cancer is very short,” he says. “Very rapidly growing cancers may go undetected, even if someone screens them annually, for example.” Also, some types of malignant tumors produce measurable signals in plasma. It does not generate, so it may not be detected by blood tests.

“We are still far from doing accurate blood-based “pan-cancer” screening tests. But it’s not impossible to achieve,” says Pritchard. “There are some big efforts underway and some promises for the future.”