Blood Test for Cancer Detects Disease Years Before Symptoms Show

Scientists have developed a blood test that can predict whether a person will have certain forms of cancer within four years, according to a study.

The test, called PanSeer, was able to detect five common types of cancer— stomach, esophageal, colorectal, lung and liver—in 88 percent of patients who were already diagnosed, with 96 percent accuracy.It also picked up cancer in 95 percent of asymptomatic people who were later diagnosed with the condition. But more research is needed to confirm this result, the authors of the paper published in the journal Nature Communications said.

PanSeer works by looking for what is known as methylation linked to cancer. Methyl groups are compounds made up of hydrocarbons that attach themselves to DNA and act as signals for turning genes on or off. Methylation describes this process.

The team drew from a study involving 123,115 people aged 25 to 90 years old who gave researchers blood samples for storage between 2007 and 2014.

From this pool, they looked at samples from 605 people without cancer, 191 of whom went on to develop either stomach, esophageal, colorectal, lung or liver cancer within the four years after they gave blood. The team also studied blood samples from 223 cancer patients, as well as 200 tumours and normal tissue.

The team looked for chemical changes in specific parts of the genetic material of the samples, called CpG islands, to find cancer in people without symptoms.

Writing in Nature Communications, the team said they wanted to emphasize that PanSeer is not for predicting patients who will develop cancer, but rather identifying those who already have growths but whose signs are picked up by current detection methods. "Many cancers do not cause the appearance of symptoms until late in disease development," they said.

The five types of cancer the test homes in on kill 261,530 people each year in the U.S.. "Early detection could greatly reduce deaths," they said.

"The ultimate goal would be performing blood tests like this routinely during annual health checkups," co-author Kun Zhang, professor and chair of the Department of Bioengineering at the University of California, San Diego, said in a statement. "But the immediate focus is to test people at higher risk, based on family history, age or other known risk factors."

Professor Nicola Valeri, team leader in gastrointestinal cancer biology and genomics at U.K.'s The Institute of Cancer Research who did not work on the study, told Newsweek the authors are among a number of teams trying to find ways to identify patients at risk of developing cancer.

"Future studies are needed to confirm these findings and to address important questions including how frequently patients should be tested, when to start testing people, and if the general population should be screened or whether specific groups at higher risk for these cancers should be targeted," he said.

Pointing out the limitations, Valeri said the data was analyzed retrospectively and relies on a relatively small number of people who developed cancer.

"Another key point is whether the test can be translated to other cancer common cancer types such as breast and prostate cancer and whether the earlier detection based on the results of these test will eventually translate to a clinical benefit and longer survival for patients," he said, adding such tests are "highly needed" so doctors can treat patients before the disease has spread to different organs.

Samantha Harrison, senior early diagnosis manager at the research charity Cancer Research UK, told Newsweek: "Detecting cancers earlier when they are less aggressive and more treatable is crucial, and we're seeing increasingly more accurate blood tests being developed and trialled.

"The PanSeer test has achieved encouraging initial results. Promisingly the test may be able to detect cancer in blood samples taken years before diagnosis. But these are early results that now need to be validated in larger studies. The next milestone will be to give the test to people who don't have cancer and see if, years down the line, it does spot any new cancers earlier than current methods. If so, we might be one step closer to screening tests for cancers too often diagnosed late.

"In the meantime, if you have noticed a change in your health, or have a symptom that you're worried about, make contact with your GP [family doctor]."

This article has been updated with comment from Samantha Harrison.

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A stock image shows a lab worker labelling a blood sample. Scientists say they have created a test that can detect cancer. Getty