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

An anonymous reader quotes a report from Scientific American: For years scientists have sought to create the ultimate cancer-screening test — one that can reliably detect a malignancy early, before tumor cells spread and when treatments are more effective. A new method reported today in Nature Communications brings researchers a step closer to that goal. By using a blood test, the international team was able to diagnose cancer long before symptoms appeared in nearly all the people it tested who went on to develop cancer. […] Kun Zhang, a bioengineer at the University of California, San Diego, and a co-author of the study, and his colleagues began collecting samples from people before they had any signs that 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. Zhang and his colleagues focused on developing a test for five of the most common types of cancer: 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. The PanSeer test works by isolating DNA from a blood sample and measuring DNA methylation at 500 locations previously identified as having the greatest chance of signaling the presence of cancer. A machine-learning algorithm compiles the findings into a single score that indicates a person’s likelihood of having the disease. The researchers 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.