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NEW YORK, March 13 (UPI) -- A blood test to screen for colorectal cancer in average-risk individuals without symptoms accurately detected the malignancy in 83% of people confirmed to have the disease, a study released Wednesday showed. The study was published in The New England Journal of Medicine.
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Researchers said the blood test's accuracy rate for colorectal cancer is similar to at-home stool tests. It's a promising step, they said, to developing more accessible screening tools for catching the disease early -- when it's easier to treat.
The test would could improve upon low levels of colorectal cancer screening -- a major cause of cancer-related mortality in the United States that results in some 50,000 deaths each year.
That's because in certain populations, such as adults ages 45 to 49, fewer than half of people who are offered screening with a stool-based test or colonoscopy elect to do neither, the study's corresponding author, Dr. William Grady, a gastroenterologist at Fred Hutchinson Cancer Center in Seattle, told UPI via email.
"Blood-based screening tests are more acceptable to people than colonoscopy and stool tests and likely will increase screening compliance.," said Grady, who is the medical director of Fred Hutch's Gastrointestinal Cancer Prevention Program. "This would lead to fewer colorectal cancer-related deaths."
These findings come from the ECLIPSE study, a multisite clinical trial of nearly 8,000 people ages 45 to 84. Led and funded by Guardant Health Inc., a precision oncology company in Palo Alto, Calif., the trial validated the performance of what is called the Shield test using colonoscopy -- the gold standard of screening -- to confirm the results.
In December, Guardant Health announced that the Food and Drug Administration is tentatively scheduled to review the premarket approval application for the Shield test March 28. Currently, the cash-pay price would be $895.
"Once the test is FDA-approved, we expect Medicare coverage to follow," Guardant Health spokesman Michael Weist told UPI via email. "And we will work with private and government payers to finalize pricing, with our goal being to provide the broadest access to eligible individuals with as minimal out-of-pocket costs to patients as possible."
The test detects colorectal cancer signals in the blood from DNA that tumors shed. This is called circulating tumor DNA, and it's also being used in "liquid biopsy" tests to monitor for recurrence in people treated for cancer.
Of the 7,861 people included in the report, 83.1% of those with colorectal cancer confirmed by colonoscopy had a positive blood test for circulating tumor DNA. Meanwhile 16.9% had a negative test -- in which a colonoscopy indicated colorectal cancer but the ctDNA test did not.
The test was most sensitive for colorectal cancers, including early-stage malignancies. It was less sensitive for advanced precancerous lesions, which can progress to cancer over time.
Colorectal cancer is the second most common cause of cancer mortality in adults in the United States and is expected to account for 53,010 deaths in 2024, according to the American Cancer Society.
While death rates from colorectal cancer in older adults have declined, rates among those under age 55 have increased by about 1% a year since the mid-2000s. Current guidelines recommend that people at average risk begin regular screening at age 45.
Colorectal cancer is the third most common cancer for people under age 50, Grady said, noting that having a blood-based test available during routine doctor's visits could help more people be screened.
The blood test's sensitivity for colorectal cancer is similar to stool-based tests and lower than that of colonoscopy, which Grady still considers the most accurate screening test for colorectal cancer.
It's intended for average-risk individuals with no family history of colorectal cancer and no personal history of colorectal cancer or advanced polyps or large polyps, he said.
Grady added that the people enrolled in the trial reflected U.S. demographics, including proportional enrollment of African American/Black, Hispanic and Asian Americans populations.
"This means the results of the Shield test are generally applicable to all people living in the U.S.," he said, adding that the novel and promising technology is the basis for blood-based cancer screening under investigation for breast cancer, lung cancer and other malignancies.
The blood test represents "a clear advance" to offer patients who don't want to have a colonoscopy, but it's not a substitute for the gold-standard procedure, Dr. Harshabad Singh, an oncologist in Dana-Farber Cancer Institute's gastrointestinal program in Boston, told UPI in a telephone interview. He was not involved in the research.
"We cannot forgo colonoscopy based on these data," Singh said, adding that "colonoscopy not only identifies cancers but intervenes on advanced precancerous lesions, which this test isn't sensitive enough to identify."
Dr. Alan Venook, a professor of medical oncology and translational research at the University of California-San Francisco, told UPI in a telephone interview that "this test is an early effort, but it can be built on -- it is not a sea change at this point."
Venook added that "numerically, it is not any different from stool testing. Ideally, the study should have done both stool sampling as well as the blood sampling. There will probably be better screenings down the road."
While the test appears very promising, nearly 17 out of every 100 patients who use it and have cancer will receive a negative result, Dr. Ronald Charles, program director of the colon and rectal surgery residency at University Hospitals Seidman Cancer Center in Cleveland, told UPI via email.
"The ultimate goal is to find a test that can detect polyps and colon cancer at an early stage," said Charles, who also is an assistant professor of surgery at Case Western Reserve University School of Medicine in Cleveland. "The hope is that the test will find cancer and polyps as close as possible to 100% of the time."
Cost also is a consideration.
"This is a funded study by a company with financial interest, so some bias may exist. In the past, these types of tests have cost thousands of dollars, but it does appear that the company is trying to make the test available for about $900, which is an improvement," Dr. Sean Langenfeld, chief of the division of colon and rectal surgery at the University of Nebraska Medical Center in Omaha, told UPI via email.
"Colorectal cancer is common, deadly and preventable," Langenfeld said. Still, "many members of the general public will not follow through with stool-based screening or colonoscopy due to fears regarding the procedure and the sensitive nature of the topic."
He added, "We thus have two jobs -- first, destigmatize screening, and second, to find effective screening alternatives for those who simply refuse the currently available tests."
