Blood Test for This Cancer Shows Promise for Early Detection

A new, simpler way to screen for colon cancer could soon become the routine. Guardant Health has produced a blood test that could be administered at a regular doctor's visit to detect the third most-diagnosed cancer in adults in the US—and in a new study, the Shield test does quite well.

• Effectiveness: The research published this week in the New England Journal of Medicine involved 7,800 or so US patients who'd had both a colonoscopy and the Shield blood test. The blood test spotted colorectal cancer in 83% of the patients who had the disease, as confirmed by a colonoscopy, per the AP.
• How it works: The blood test seeks out DNA fragments that both cancerous cells and precancerous growths shed.
• Current methods: The gold standard for colon cancer screening at the moment is the colonoscopy, typically administered every 10 years. Or, patients can get a fecal test every one to three years. Both options can be offputting, which doctors feel can cause reluctance to get screened. "Either you take this horrible laxative and then a doctor puts an instrument up your behind, or you have to manipulate your own poop," one gastroenterologist tells the New York Times.
• Caveat: The blood test doesn't do as well in detecting precancerous growths called polyps—it only picked up about 13% of them. The fecal test, meanwhile, detects them 43% of the time, while a colonoscopy picks up 94%. There was also a false positive rate of 10% with the blood test, which could cause undue stress on its own.
• The numbers: Colon cancer is the second-leading cause of cancer deaths in the US, with 153,000 cases expected this year and 53,000 fatalities. More patients coming in to be screened could prevent some of those deaths. It's recommended that people age 45 and up get screened.
• Status: The blood test is already available in the US, though it's not yet FDA approved (Guardant hopes for that OK later this year). The $895 price tag could also be a roadblock, as most insurers don't cover it. However, a Guardant spokesperson tells the Times it will work with Medicare and Medicaid to "finalize pricing" once the blood test gets the FDA thumbs-up.

(More colon cancer stories.)