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A new blood test to detect colorectal cancer could give patients important insight into their health at low cost after receiving the Food & Drug Administration’s approval this week.
A new blood test to detect colorectal cancer could give patients some important insight into the status of their health at low cost after receiving the Food and Drug Administration’s approval this week.
Produced by Guardant Health, the “Shield” test detected roughly 83% of colorectal cancers, with about a 10% false positive rate, according to Reuters. It works by detecting the DNA from cancerous tumors that show up in a person’s blood. Another non-invasive at-home test, Exact Sciences’ stool “Cologuard” test, was previously shown to find roughly 92.3% of colorectal cancers.
Doctors had already been using the Shield test, but now patients can seek reimbursement from insurers for the test. The company said it’s intended “as a screening test for individuals at average risk for the disease, age 45 or older, and is not intended for individuals at high risk for colorectal cancer.”
It’s a welcome development, experts say, as data from the American Cancer Society shows that there has been a considerable rise in colorectal cancer among people younger than 50. Such cancers are now the leading cause of cancer death in men younger than 50, and the second-leading cause in women that age.
Neil Maniar, a Northeastern University professor of public health practice, says the Shield test is an important step in determining whether a person should have a colonoscopy, a procedure considered the gold standard in diagnosing colorectal cancer.
Northeastern Global News spoke to Maniar about how people can get their hands on the test, who is eligible and what to do if they receive a positive result.
We’re seeing an increase in the incidence of colorectal cancer in younger populations, which is why there was a change in the screening guidelines to 45 years of age as opposed to 50 for colonoscopy. Unfortunately, despite this change in guidelines, we are also seeing rising rates of colorectal cancer among individuals younger than 45, which underscores the importance of other screening tools.
With these new tests, I think the more opportunities that individuals have to screen for colorectal cancer — the more modalities and options that they have — the better, especially for a test like the one that was just approved. Because it has received FDA approval, this is really the only blood test for colorectal cancer that will be potentially covered by insurance and by Medicaid and Medicare, which is a big thing because it’s about a $900 test. So if it’s covered by insurance, that will hopefully increase the likelihood that people take this test, especially those who are not able to get a screening colonoscopy.
What makes colorectal cancer somewhat unique among cancers is that it is in a relatively small group of cancers where we actually have the opportunity to prevent the cancer through screening. Screening is really about trying to detect cancer early, right? And with colorectal cancer, because a large percentage of colorectal cancers start off as a polyp, the only way that you can detect a precancerous polyp and remove that polyp is through the colonoscopy, which is why it’s really important for individuals to get their colonoscopy once they’re 45, or even earlier if they have a medical need to get a colonoscopy.
Screening tests such as Cologuard and similar tests are fecal occult blood tests, which detect blood in the stool. Now we have a blood test that will detect cancerous DNA in the blood. There are opportunities to catch cancers at a much earlier stage if individuals get screened in a timely manner. A positive result from any of these tests will require a colonoscopy for a formal diagnosis. The availability of other colorectal cancer testing options is important because the colonoscopy is an invasive procedure; it’s a screening test that requires a lot of prep; it is disruptive to schedule, and you need someone to drive you home after the test. So there are a lot of logistics around the colonoscopy that can make it very challenging. Adding this new test to the menu of options that people have in terms of colorectal screening can play a key role in increasing colorectal cancer screening rates and reduce disparities in colorectal cancer screening.
The more that we can increase the percentage of the population that is screened for colorectal cancer, the better. The other thing about colorectal cancer: if detected early, colorectal cancer is actually quite treatable; if detected late, it becomes very hard to treat — the mortality rates go up significantly. Here again we have a really good portfolio of screening tests that can help detect cancer early, so it’s a really positive thing for everyone.
This test in particular is going to be helpful for individuals who meet the age threshold (45 or older) who may just feel like they want to get a screening test and don’t want to get a colonoscopy, or aren’t eligible for one. This is a good option for them.
A screening for colonoscopy is for people 45 and older, and I believe there are some instances where it could be under age 45 if there is a strong family history or other risk factors that are present. A diagnostic colonoscopy is where a clinician finds either symptoms or other indications that are concerning and they want to get a colonoscopy to make a formal diagnosis. If somebody has symptoms, then that could trigger the need for a diagnostic colonoscopy, which in many cases could be covered by insurance.
There are a number of conditions that can cause blood in the stool. But if you have a positive test from a Cologuard test, the next step is to get a colonoscopy as a follow-up. Similarly, with this blood test, which would detect the DNA, if you have a positive result, the next step would be to get a colonoscopy.
If somebody has symptoms, it’s really important talk to their clinicians to assess what might be going on.
There is another blood test that is on the market that is not currently approved by the FDA. A big part of the reason for that is the number of false positives and the overall accuracy of the results.
It’s important to note that for all of these tests, there will be a risk for false positives. As I said, there are a number of possible causes for blood in the stool, and that’s what the fecal occult blood tests are trying to measure. The accuracy for this new blood test is higher than the other ones that had previously come on the market, but there is still the possibility of a false positive. This is why, if there is a positive result, a colonoscopy is required to confirm the result. A colonoscopy is the gold standard; it is the best way to determine whether there is a problem.