The Food and Drug Administration approved on Monday 'Guardian Health'The blood test, called Shield, is used to detect colon cancer. The test is not intended to replace colonoscopies, but it is generating excitement among doctors, who say it has the potential to boost the discouraging detection rate for the second leading cause of cancer death in the United States.
Shield was already available to physicians as a screening tool, with an out-of-pocket cost of $895. With FDA approval, Medicare and private insurance companies are much more likely to cover the cost of the blood test, making it more accessible to patients.
Dr. Arvind Dasari, an associate professor in the department of gastrointestinal and medical oncology at the University of Texas MD Anderson Cancer Center, called the approval a “positive development.”
But, he cautioned, “we will have to wait and see what the impact will be in terms of improving detection and reducing the incidence of mortality.”
The American Cancer Society estimates that more than 53,000 people will die from colorectal cancer this year.
Research published in March showed Shield is 83% effective at detecting colorectal cancers. It works by detecting DNA that cancerous tumors release into the bloodstream.
It is more effective at detecting cancers at later stages, when tumors release more DNA. The study found that Shield only detected 13 percent of polyps at earlier stages.
Testing should be performed at least every three years, starting at age 45, the same age at which colorectal screening is recommended to begin.
A positive result is not necessarily a diagnosis. If the results indicate cancer, patients will still need a colonoscopy so doctors can see where the tumors are located and how far they have progressed.
“People need to understand that for a positive Shield test to come back, you need to have a colonoscopy to confirm that you have an advanced lesion or colorectal cancer, or that the results were false,” said Robert Smith, senior vice president of Cancer Early Detection Science at the American Cancer Society. “A test like this is not complete if it comes back positive and you haven't had a colonoscopy.”
This is the second blood test to detect colon cancer; Epigenomics’ Epi proColon was approved in 2016. But it is rarely used, Smith said, because of concerns about its accuracy. It is also not covered by Medicare or private insurance.
Since the mid-1990s, there has been a worrying rise in colon cancer cases in people under age 55, with an increase of 1% to 2% per year in that age group. At the same time, cases and deaths among adults age 60 and older have been declining, according to the American Cancer Society.
“What breaks my heart is that it's preventable,” said Dr. William Grady, a gastroenterologist at Fred Hutchinson Cancer Center in Seattle. “One of my greatest joys is when I get a colonoscopy and I can remove polyps” that, if left untreated, would have progressed to cancer.
In fact, colorectal cancer is one of the few cancers that can be prevented with screening, and colonoscopy is by far the most accurate way to detect it. However, screening rates are extraordinarily low: less than 60% of eligible people have undergone the recommended screening tests.
“The biggest problem with colon cancer today is that there is a significant portion of the population that is not being screened,” said Dr. Sapna Syngal, director of strategic planning for cancer prevention and early detection at Dana-Farber Cancer Center in Boston. “If this test increases the number of people who are being screened, it will have a huge impact.”
Grady, who led the March study of the Shield test, said it is often adults in their 40s and 50s who are least likely to comply with screening.
“These are people who have jobs, many have families, and so they have all these other life responsibilities that prevent them from taking care of themselves,” she said.
Colonoscopy is a time-consuming operation that forces people to take at least a day off work. Plus, there's a certain “ick” factor that many people find unpleasant. During the procedure, doctors insert a small camera into the rectum to look for tumors or spots that may become cancerous in the future.
This camera needs a clear view of the colon. The day before the colonoscopy, patients have to take a strong dose of laxatives, meaning they spend a lot of time in the bathroom.
“A lot of people don't like the messiness of handling stool, and a lot of people really don't like colonoscopy, especially the prep,” said Electra Paskett, associate director of population sciences and community outreach at Ohio State University's Comprehensive Cancer Center. “I think a blood test would be ideal for a lot of people.”
Another method of colon cancer screening includes fecal occult blood tests, which detect blood in the stool, which can be a warning sign of colon polyps or cancer. FIT-DNA tests, such as Cologuard, are highly effective at detecting cancer, but are less effective at detecting precancerous polyps.
John Gormly, 77, of Newport Beach, California, had avoided colonoscopy for years. When his doctor offered him the option of taking the Shield blood test, he took it.
“He called me a day later and said, 'I don't like the results at all. I'm going to send you for a colonoscopy,'” Gormly recalled. “It turned out I had stage 2 colon cancer.” Surgeons were able to remove the tumor completely.
“Thank God I got the blood test done,” Gormly said. “I never felt anything, I never knew anything was wrong. Without that blood test, I don't know how it would have turned out.”
