4 years before the first symptoms
A test has been created that detects cancer by blood four years before its manifestation
Scientists from the USA and China have developed a method that allows blood tests to detect five forms of cancer four years before the first signs appear, writes the journal Nature Communications (Chen et al., Non-invasive early detection of cancer four years before conventional diagnosis using a blood test).
The test, called PanSeer, effectively detects cancer of the stomach, esophagus, lung and liver, as well as colorectal cancer at the earliest stages. Blood samples for the study were collected as part of a study conducted by Fudan University in China in the period from 2007 to 2017. It was attended by more than 120 thousand people, each of whom for ten years passed blood tests and underwent regular checks with doctors. In total, during this time, scientists have collected more than 1.6 million samples, which are now stored in the university archive. The uniqueness of the study was that specialists had access to the blood of cancer patients taken long before they were diagnosed with cancer by traditional methods.
The researchers were able to study samples of both healthy and sick people from the same cohort. They analyzed plasma samples from 605 asymptomatic individuals, 191 of whom were later diagnosed with cancer, 223 samples from cancer patients with a confirmed diagnosis, as well as 200 samples of primary tumor and normal tissue.
This allowed the authors to identify markers of early cancer development in the blood and develop a test based on them. As a result, the new method revealed cancer in 91 percent of cases in people who had no symptoms when a blood test was taken, and the diagnosis was made only after one to four years. With a 95 percent probability, the test determined the absence of cancer. For patients who had already been diagnosed with cancer at the time of blood collection, the probability of detection by early markers was 88 percent.
Thus, the authors note that the PanSeer test is effective precisely for detecting cancer in the early stages, when other methods are powerless. Early detection is very important because the survival rate of cancer patients increases significantly when the disease is identified in the initial stages, when the tumor can be surgically removed or treated with appropriate medications.
"The ultimate goal is to use the test for regular blood tests during annual medical examinations," said the author of the article, Kun Zhang, professor and head of the Department of bioengineering at the University of California, San Diego (in a press release, Non–invasive blood test can detect cancer four years before conventional diagnosis methods – VM).
According to him, the immediate goal is to test people at higher risk based on family history, age or other factors.
The researchers emphasize that the PanSeer analysis does not predict who may develop cancer and who may not. It identifies patients who already have cancers, but they remain asymptomatic for modern detection methods.
Zhang and his lab have been developing cancer detection methods based on a biological process called DNA methylation analysis for more than a decade. The method verifies a specific DNA signature called CpG methylation, which is the addition of methyl groups to multiple adjacent CG sequences in a DNA molecule. Each tissue in the body can be identified by the unique signature of methylation haplotypes.
The authors hope that the test they developed will be widely used for early screening of the five most common types of cancer.
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