Scientists devise blood test that detects cancer years before it turns symptomatic

The cancer burden in India is on the rise, with as many as 7.84 lakh deaths due to the disease recorded in 2018

Early detection of malignancy is the key to reducing cancer mortality and scientists have been trying for years to create a way to detect the disease before the tumour cells spread.

Finally, a group of scientists have come up with an experimental blood test that could diagnose cancer in patients much before the symptoms appeared. The research findings were published in the journal Nature Communications.

As per Kun Zhang of the University of California, who is a co-author of the study, the blood samples of people who eventually developed cancer later had telling signatures that could establish they would get cancer.

In the past, researchers have focused on collecting blood samples of people who have already been diagnosed with cancer. This was the first time scientists began collecting samples of people who had not been detected with cancer yet.

More than one lakh healthy individuals from China were recruited by researchers in 2007 to undergo annual health check-ups. Of these, nearly 1,000 participants developed cancer within the next 10 years.

The scientists got down to devising a blood test for the five most common types of cancer: lung, esophageal, colorectal, stomach, and liver. The PanSeer blood test was developed to detect the methylation pattern in the samples, since abnormal methylation is usually a signal of multiple types of cancer, such as pancreatic and colon cancer.

They tested blood samples of 191 participants, who eventually developed cancer, were compared with blood samples of healthy individuals. By comparing the results of both, they could detect cancer in people almost four years before the first symptoms appeared. The test results were found to be 90 percent accurate.

However, even if blood tests to detect cancer become available, in all probability, they will only be able to detect a few types of cancer before they become symptomatic. This is because some cancers have an exceptionally long lead time while others have noticeably short lead time. There is also a chance that some cancers may never get detected through blood tests despite annual screening because they do not produce enough signals in blood plasma.