Guardant Shield – a new blood test to screen for colorectal cancer was recently approved by the U.S. Food and Drug Administration. The decision came after a study of more than 7,500 people found that Shield detected about 83% of colorectal cancers.
Colorectal cancer is among the most common cancers, and it is on the rise among younger people. If it is caught in the early stages, colorectal cancer can generally be treated effectively. Unfortunately, many cases of colorectal cancer aren’t diagnosed until their later stages, when treatment is more challenging, and outcomes are generally worse. People waiting too long to get colonoscopies is one contributing factor to the rates of advanced colorectal cancer, and health experts hope that this blood test could encourage more people to be screened.
“We know there are many eligible patients who do not get screened for colon cancer currently in the United States. The availability of a non-invasive screening test that does not involve handling stool may allow us to reach many more people and expand access to screening, which is huge and exciting,” says Capital Digestive Care gastroenterologist Dr. Barathi Sivasailam.
How accurate is it?
The test is a simple blood draw. Its accuracy is about the same as fecal immunochemical tests (FIT) such as Cologuard. Shield had a false negative rate of 16.9% and returned false positive results 10% of the time. Shield is approved for adults aged 45 and over who are at average risk of developing colorectal cancer.
“It is important for patients to understand the limitations of the blood test. There are still false positives and false negatives and it does not do a good job at finding smaller polyps,” explains Dr. Sivasailam. “In addition, colonoscopy is the only test that can actually prevent colon cancer by removing small polyps before they grow into cancer.”
How Shield compares to colonoscopy
Colonoscopy remains the gold standard in colorectal cancer screening, and for good reason. Not only is it more accurate than other screening tests like FIT or Shield, but it is the only test that can help prevent colorectal cancer as well as diagnose it. During a colonoscopy, providers can remove polyps (growths) before they become cancerous. It can also detect a variety of precancerous lesions in the colon, which can be treated before turning into cancer.
For those who may be putting off scheduling a colonoscopy because you’re concerned about the test or the preparation required the day before, you might be surprised to learn that there are a variety of options available to make colonoscopy prep easier and more comfortable.
Overall, any test that makes it easier for more people to get some kind of colorectal cancer screening is good news – getting screening done can save your life, even if it’s a less accurate test. However, colonoscopy is still the best tool for detecting and preventing colorectal cancer.
“At the end of the day we do want our patients to get screened and this will hopefully help that happen. We always encourage speaking to a gastroenterologist about your specific history and symptoms to ensure that you are picking the right modality of screening for your individual case,” says Dr. Sivasailam.
Talk with your healthcare provider about your concerns and find out about the latest colonoscopy options.