FDA Approves Blood Test to Detect Colon Cancer

The U.S. Food and Drug Administration (FDA) has approved a blood test to screen for colorectal cancer in individuals aged 45 and older with an “average risk” of colon cancer. The blood test, known as Shield and manufactured by Guardant Health, is already commercially available, but FDA approval will help broaden availability and insurance coverage.

Shield detects colorectal cancer by detecting DNA shed by tumors in blood samples. Results take about two weeks after the samples are received by the laboratory. However, specialists warn that the blood test is not an equivalent alternative to colonoscopies, but it could lead to more people getting screened since it takes less time and effort to get screened. Colonoscopies are more accurate at detecting cancer, allow for the removal of precancerous polyps and are recommended every 10 years instead of every three years for the blood test.

In clinical trial, Shield was found to have an 83.1 percent sensitivity rate, meaning 83.1 percent of patients with colorectal cancer detected by a colonoscopy tested positive on the Shield blood test. It also had an 89.9 percent specificity rate, meaning 89.9 percent of patients without cancer tested negative on the blood test. Yet, despite the high overall sensitivity rate, the clinical trial data indicated Shield may miss one in 10 people who have precancerous lesions and one in 1,000 people with cancerous lesions. These “false negatives” may result in tests finding no evidence of cancer, but patients actually have precancerous or cancerous lesions.

“The FDA approval of the Shield test is a significant victory for patients and an important milestone in Guardant Health’s mission to conquer cancer with data. Shield can help improve colorectal cancer screening rates so we can detect more cancers at an early stage, when they are treatable,” said AmirAli Talasaz, Guardant Health co-CEO. “We are now getting ready to launch this test in the near future and are very excited to empower physicians with a viable blood-based screening option to tailor the screening regimen to the unique needs of their patients.”