The Food and Drug Administration (FDA) has approved a new blood test to detect colon cancer. The blood test, manufactured by Guardant Health’s Shield, does not replace colonoscopies. Colorectal cancer is the fourth most common cancer in the United States, with 1 in 23 men and 1 in 25 women having a lifetime risk of being diagnosed. The risk is higher for African Americans. According to the Surveillance, Epidemiology, and End Results (SEER) program, Black Americans have an incidence rate of 41.9 per 100,000, compared to 37.0 per 100,000 for white Americans. Black Americans are also 35% more likely to die from colorectal cancer than non-Hispanic whites.
The new test is welcome news, especially for the Black community, because screening rates for colon cancer for eligible people are very low. With FDA approval, Medicare and private health insurance companies are more likely to cover the cost of the test, thereby increasing access for many.
The hope is that access to this test will increase the number of people being screened, thereby increasing detection rates. Jaques Beavis, MD, a gastroenterologist at Memorial Sloan Kettering, says, “for Black and Brown communities who have historically been marginalized from obtaining equitable levels of healthcare for various reasons, a blood test can serve as a particularly effective way in engaging them to participate in colon cancer screening since the test is done in a way all patients are familiar with.” Beavis, however, has reservations about the test’s impact on colon cancer rates overall. The new screening test developed by Guardant detects DNA shed from cancerous cells found within the colon. The data shows that it is 83% effective at detecting colon cancer but falls very short when it comes to detecting precancerous polyps. “The concern with the Guardant test is that if it becomes widely used, its significant inability to adequately detect precancerous polyps may lead to an increase in colon cancer rates overall,” cautions Beavis. The Guardant test would need to be administered at least every three years starting at age 45, which is the current age that colonoscopies are recommended.
The American Cancer Society still recommends the colonoscopy as the gold standard for detecting colon cancer.
