A simple blood test can detect colorectal cancer early, study finds

At a time when colorectal cancer is on the rise, a new study finds the disease can be detected through a blood test.

The results of a clinical trial, published Wednesday, in The New England Journal of Medicine, show that the blood-based screening test detects 83% of people with colorectal cancer. If the FDA approves it, the blood test would be another screening tool to detect the cancer at an early stage.

The test, developed by Guardant Health, can be done from a blood draw. The company says its test detects cancer signals in the bloodstream by identifying circulating tumor DNA.

Dr. Barbara Jung, president of the American Gastroenterological Association, says the test could help improve early detection of colorectal cancer.

"I do think having a blood draw versus undergoing an invasive test will reach more people," she says. "My hope is that with more tools we can reach more people."

But even if the blood test is approved, it will not replace the dreaded colonoscopy. "If the test is positive, the next step will be a colonoscopy," Jung says. That's because a colonoscopy can detect precancerous lesions — called polyps.

"And when you find those, you can also remove them, which in turn prevents the cancer from forming," Jung says.

The U.S. Preventive Services Task Force recommends regular screening should begin at age 45. But approximately 1 in 3 eligible adults are not screened as recommended, according to the American Cancer Society.

"Over 50 million eligible Americans do not get recommended screenings for colorectal cancer, partly because current screening methods are inconvenient or unpleasant," Guardant Health CEO, AmirAli Talasaz, wrote in a release about the results of the study.

Currently, effective screening options include stool tests and colonoscopies.

"It's never been easier to get the screening," T.R. Levin, a gastroenterologist at Kaiser Permanente told NPR last year.

Some of the early symptoms of colorectal cancer can include blood in your stool, a change in bowel habits, weight loss for no known reason, a feeling of bloating or fullness and fatigue. If you experience any of these symptoms, you should talk to your doctor.

And while colorectal cancer is still rare in young adults, the rate has been increasing. About 20, 000 people in the U.S. under the age of 50 are diagnosed each year.

"Colorectal cancer is rapidly shifting to diagnosis at a younger age," conclude the authors of an American Cancer Society report released last year. Since the mid-1990s, cases among people under 50 have increased by about 50%. It's one of the deadliest cancers in this age group.

Guardant Health has already filed for approval with the FDA. The decision is expected to come later this year.

This story was edited by Jane Greenhalgh.

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