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Colon or colorectal cancer (CRC) is the third leading cancer in both men and women in the U.S., and the of cancer death. Meanwhile, screening for CRC is both effective and cost-effective in preventing colon cancer and related deaths. Further, we have multiple long-established screening options, the most commonly used being either a colonoscopy or stool-based testing with either fecal immunochemical testing (FIT) or multi-target stool DNA test (mt-sDNA).

So, what's the problem? Despite available modalities, screening rates in the U.S. are too low. With new guidelines lowering the age to initiate CRC screening to 45, only 59% of screening-eligible individuals are up to date on screening -- leaving nearly 50 million adults in the U.S. that are in need of screening. How to boost this rate to 80% or higher has been the focus of decades of public health work.

This is where a new type of test comes in. FDA recently approved the first blood test for colon cancer screening in adults ages 45 and older at average risk for the disease. Could this hold the key to higher screening rates? While the approval is encouraging, there are some drawbacks and other considerations.

First, let's examine some of the issues with traditional CRC screening.

The issues with adherence are complex and multi-faceted, but one tangible aspect is patient preference. Many patients abhor colonoscopy for the preparation involved, time off from work, risk of complications, and use of anesthesia. The logistics of colonoscopy can be challenging as well, as it is a limited resource and can be difficult to schedule, and often requires travel and a driver. Meanwhile, stool-based testing is non-invasive, readily available, carries no risks, and can be done in the comfort of the patient's home and mailed in. However, patients dislike handling anything to do with stool, and at home the kit may get lost or forgotten.

As a result, the promise of a blood test for colon cancer has always held appeal for being a simple collection, with virtually no risks, and the blood draw can be coupled with other routine or preventative blood work, completed right in the doctor's office. have demonstrated higher adherence to a blood test compared to a stool test, and suggest the lofty goal of 80% or higher adherence may be achievable.

With the FDA approval of Guardant's Shield blood test last month, we are at the brink of seeing the potential of a blood test become reality. The test has 83% sensitivity for CRC and 90% specificity for advanced neoplasia. However, the sensitivity of detecting advanced precursor lesions is just 13%. The test characteristics meet the national coverage decision to pay for the test .

The FDA approval of the blood test has brought mixed reactions from clinicians. Proponents are excited about offering a convenient modality that patients will be more likely to agree to and complete in higher numbers. The yield from the test will dictate the need for a colonoscopy or not. Opponents see it as an inferior screening test to colonoscopy or even stool-based test options. They worry that it will cannibalize colonoscopy screening -- the most sensitive and complete test for colon cancer screening -- instead of bringing additional people in for screening.

Broadly, where both sides agree is that a blood test with performance at par with current stool tests, offered in the right infrastructure to bring additional people in for screening, is a good thing. It has the potential to get us closer to our screening goals and steadily increase colonoscopy volumes, which would be performed as a second step when the test is abnormal.

Of course, there are many details yet to be worked out that will affect uptake of the blood test, but the time is now for clinicians and healthcare systems to start thinking about whether the test has a role for their patients. Do they need a boost in adherence, and if yes, will their patients sign up and complete a blood test if they are offered one, instead of a colonoscopy or stool test? Will it help in screening rates by , , geography, language, and , or potentially widen them? What's the best way to communicate information about the blood test to patients in a manner that will boost uptake?

While many questions remain, a few things are fairly certain. First, healthcare systems and clinics need to offer at least one non-invasive screening modality in addition to colonoscopy. Second, they need to develop organized screening programs with some form of outreach and quality assurance for completion of the screening continuum (either colonoscopy alone or non-invasive test followed by colonoscopy if abnormal). Lastly, they need to prepare their clinicians to have answers ready when patients ask about the new blood test for colon cancer screening.

FDA has done its part in approving this encouraging new test for CRC. It's now up to individual physicians and healthcare systems to pave the way for patient uptake. It's high time to boost those screening rates.

is the Robert M. and Mary H. Glickman Professor of Medicine and Gastroenterology and the director of outcomes research in the Division of Gastroenterology & Hepatology at NYU Langone in New York City. She is a practicing gastroenterologist and researcher in colon cancer screening and quality indicators of colonoscopy. She is on the editorial board for 番茄社区 Medical Today.

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