Experts are hoping that FDA approval of the first colon cancer screening blood test – which has several opponents – will boost low screening rates in the US, where colorectal cancer (CRC) is the third leading cancer and the second most cause of cancer death, but say co-operation is needed by the healthcare sector.
Screening is both effective and cost-effective in preventing colon-colorectal cancer and related deaths, writes Dr Aasma Shaukat in Medpage Today, and there are multiple long-established screening options, the most common being either a colonoscopy or stool-based testing with either faecal immunochemical testing (FIT) or multi-target stool DNA test (mt-sDNA).
So, what’s the problem? Despite available modalities, screening rates in the US are still too low.
With new guidelines lowering the age to initiate CRC screening to 45, only 59% of screening-eligible Americans are up to date on screening – leaving nearly 50m adults 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 the new test comes in – and with the FDA approval of this for colon cancer screening in adults 45 and older at average risk for the disease, the question is: could it hold the key to higher screening rates?
While the approval is encouraging, there are some drawbacks and other considerations.
First, regarding 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 work, risk of complications, and use of anaesthesia. The logistics of colonoscopy can be challenging as well, as it is a limited resource and can be difficult to schedule. It often requires travel and a driver. Meanwhile, stool-based testing is non-invasive, readily available, risk-free and can be done in the comfort of the patient’s home.
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. Plus, the blood draw can be coupled with other routine or preventative blood work, in the doctor’s office.
Randomised studies have shown higher adherence to a blood test than a stool test, with studies on patient preference suggesting 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 on 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. The sensitivity of detecting advanced precursor lesions, though, is just 13%.
Mixed reactions
Proponents are excited about offering a convenient modality to which patients will be more likely to agree and complete in higher numbers, and the yield from the test will dictate the need for a colonoscopy or not.
Opponents, though, see it as an inferior screening test to colonoscopy or even stool-based test options. They worry that it will cannibalise colonoscopy screening – the most sensitive and complete test for colon cancer screening – instead of bringing in additional people for screening.
Broadly, both sides agree that a blood test with performance on par with current stool tests, offered in the right infrastructure to increase numbers of people 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.
Many details still have 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 close the disparities in screening rates by race, ethnicity, geography, language, and socioeconomic status, or potentially widen them? What's the best way to communicate information about the blood test to patients in a way to boost uptake?
While many questions remain, some 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 organised screening programmes 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).
Last, 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.
Aasma Shaukat, MD, MP, 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.
Medpage Today article – Blood Test for Colon Cancer: Panacea or Hype? (Open access)
See more from MedicalBrief archives:
FDA green light for colon cancer blood test
Updated US guidelines for colorectal cancer screenings
Vital early signs of colon cancer in young adults – US study