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
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
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.
"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
In December,
"Once the test is FDA-approved, we expect Medicare coverage to follow,"
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
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
"This means the results of the Shield test are generally applicable to all people living in the
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
"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.
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.
"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
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
"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."
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