An estimated 52,500 Americans died from colon cancer last year; However, the disease is highly treatable if detected early.
Prevention and primary care experts at the U.S. Preventive Services Task Force recommend that adults ages 45 to 75 be screened for colon cancer.
The most common test to detect colon cancer is a colonoscopy, which is performed once every ten years. However, there are simple methods that can detect symptoms of diseases in a person’s stool. And new prescription blood tests are coming. Researchers and manufacturers say such simple tests could encourage more Americans to get tested.
The tests are less invasive and time-consuming than colonoscopies, are often less expensive, and can improve detection rates. Nationally, nearly 2 in 5 eligible adults were not up to date with colon cancer screening in 2021, meaning they were unaware of their risk for the second-deadliest type of cancer.
“There are many patients who do not want or do not have access to a colonoscopy,” said Dr. Asma Shaukat, a gastroenterologist at NYU Langone Health.
Two stool tests that are now available are less expensive and easier to complete than colonoscopy: Cologuard and the fecal immunochemical test, or FIT. The first of two new blood tests could hit the market in 2024 and could expand who is tested, Shaukat said.
Blood tests could be done in 2024.
Guardian Health, a Silicon Valley company, has developed a DNA blood test called Shield that primary care doctors can prescribe.
Guardian is seeking approval from the Food and Drug Administration, which has scheduled an advisory committee hearing for March 28.
Last year, the Guardian published the results of a study of 20,000 adults that showed the Shield test identified 83% of colon cancer cases across all stages of the disease. The study detected all advanced-stage cancers, while the test detected 55% of stage one cancers and 13% of precancerous polyps and other lesions.
Colonoscopies have the highest detection rate of 95%. Cologuard, which looks for high-risk genetic mutations in stool samples, can detect 92 percent of colon cancers. FIT detects 74% of colon cancers with a single test, but the test is done annually and can detect more cancers over time.
Amir Ali Talasaz, co-founder and co-CEO of Guardant, said SHIELD testing will be recommended every three years, which is more frequent than a once-a-decade colonoscopy.
“As long as patients have our test every three years, colon cancer cases will be detected at an early stage,” Tulsaz said. They noted that survival rates are greater than 90 percent when colon cancer is detected early.
Talasaz anticipates that the test will be of interest to people who have not been screened for colon cancer and do not want to undergo an invasive colonoscopy. In a non-peer-reviewed paper presented at a scientific conference, the company cited internal data showing that when a doctor orders a blood test, the patient receives the test in more than 90 percent of cases.
Prevention experts say that if doctors order a test, it is important for patients to follow it. Patients often delay or avoid doctor-prescribed colonoscopies, forcing them to follow a clear liquid diet and take liquid laxatives the day before.
“The best screening test is the one that is finally done,” Tulsaz said. “That’s really the opportunity: to increase overall compliance with colorectal cancer screening.”
Will Medicare and other insurers cover blood tests to detect colon cancer?
Guardant has marketed Shield as a lab-developed test on a limited basis to employers and other customers, Talasaz said. Price: $895.
If the FDA approves the test, the next step is to get Medicare to pay for the test. The federal health program for adults 65 and older has already said it will cover blood screening tests for colon cancer that meet performance thresholds.
If the company receives FDA approval, Talasaz said the Medicare reimbursement rate “will really impact how we price the test,” but he expects the amount to be “comparable” to stool-based tests. “approximately” and less expensive than colonoscopy.
The U.S. Preventive Services Task Force, an independent advisory panel that reviews tests, treatments and medical services, has not reviewed the SHIELD blood test.
Under the Affordable Care Act, insurers must cover preventive care that has been assigned an “A” or “B” rating by the task force. The task force assigned an “A” grade for colon cancer screening to adults ages 50 to 75 and a “B” grade to those ages 45 to 49.
ACA plans must cover a screening colonoscopy once every 10 years and a FIT test every year, among other screening tests.
The amount doctors and hospitals charge for a colonoscopy can vary widely. A December study in JAMA Health Forum found that hospitals charged an average of $1,530 in copays for colonoscopies, far more than the $989 billed by surgery centers on the same day. While screening tests must be covered under the ACA, many patients incur additional charges, such as sedation and polyp removal. All charges add up to thousands of dollars.
SHIELD testing had not yet begun when the task force updated colon cancer screening coverage in 2021. Task forces typically take five to seven years to update screening recommendations. That means Shield and other blood tests probably won’t be evaluated before 2026.
Freenome Holdings is evaluating another blood test in a study that will collect blood samples from patients undergoing colonoscopies. The company hopes to report results by spring 2024, said Shaukat, the study’s principal investigator.
How do the new blood tests compare to stool tests?
Experts not affiliated with the Guardian aren’t sure blood tests will gain traction. They say it will be difficult to make progress with the medical community and that consumers have been slow to adopt colonoscopy-free screening.
The FIT, a test that detects blood in stool, has been available since the late 1990s, but did not become popular with the public until the late 2000s, said Dr. Thomas Imperial, professor of gastroenterology and hepatology at the Indiana University School of Medicine. Medicine There was no interference.
Although the test is widely used in Europe, it has been slow to gain popularity in the United States market, outside of large organizations such as the Veterans Administration and Kaiser Permanente.
Experts say options other than colonoscopy will be critical to reaching the medical community’s goal of achieving an 80 percent colon cancer detection rate.
Will a blood test detect polyps?
The medical community will closely monitor the results of a handful of clinical trials that will compare annual or biannual use of FIT testing with once-a-decade colonoscopy. The Veterans Administration is conducting a study.
Imperial said the SHIELD test could be a convenient option for doctors when they already plan to draw blood for other medical reasons. He worries that doctors and patients won’t be able to discuss in detail the pros and cons of self-administered blood tests, along with other screening options.
“This test (Shield) is fine for detecting colon cancer, but it will not detect early polyps, especially advanced ones that are easily removed by colonoscopy,” Imperial said. “You won’t spot them except when they get into mischief.”
Clinical studies show that the shield detects 13% of precancerous lesions.
Shaukat, director of outcomes research at NYU Langone, said she envisions the blood test as a “second option” behind colonoscopies and stool tests. For example, blood tests may be appropriate for adults around age 40 who are reluctant to undergo a colonoscopy or stool test, Shaukat said.
She said there is “a lot of work to be done” to improve screening among people aged 45 to 49. Tests like FIT and Cologard are simple, she said, and she believes blood tests could also improve detection rates.
Dr. Barnett Kramer, retired director of the Division of Cancer Prevention at the National Cancer Institute and a member of the Lisa Schwartz Foundation for Truth in Medicine, said FIT tests are relatively inexpensive and supported by evidence. These stool tests can also be done at home and sent to a laboratory. FIT also does not have the rigorous preparation or potential harm of a colonoscopy.
Although blood tests will soon become more widely available, Kramer said they are not yet proven.
For blood tests, “a significant amount of work needs to be done to achieve the same strength of evidence,” Cramer said.
Possible References Used
