Given that a colonoscopy is three days of no solids and a camera inserted through the rectum and into the nether regions, it’s no surprise that many folks skip colon cancer screening. A full one-third of American adults avoid the procedure and thus increase risk of colorectal cancer – the second-leading cause of cancer deaths. But a new, highly accurate and less invasive test may soon change much of that.
This new test may set the standard for the future of colon cancer screening, according to a study released this month, which documents it has a 90% accuracy rate. That’s even higher than what you’d expect with a colonoscopy, which is in the 60%-70% range.
The benefit of this new test is that it’s both convenient and accurate. The FDA has noticed too, and approved the test last month in the hope it would appeal to adults who would otherwise not get screened.
Colon cancer is the most common form of colorectal cancer, with roughly 143,000 new cases of the latter diagnosed each year and roughly 50,000 annual deaths in the U.S.
Traditional Colon Cancer Screening
This new test is a form of at-home stool testing. It’s one of three broad forms of colon cancer screening approved by the U.S. Preventative Services Task Force (USPST), which recommends one of or a combination of the following:
High Sensitivity Fecal Occult Blood Test (FOBT) – A home test, in which the patient swipes stool on a sample and sends it to a lab where it’s analyzed for blood and DNA.
Flexible Sigmoidoscopy – Less intrusive than a colonoscopy, a sigmoidoscopy involves a microscopic tube inserted through the rectum and into the left side of the colon. It’s less intrusive because it takes less preparation than a colonoscopy and does not examine the entire colon.
Colonoscopy – This consists of a flexible tube with a fitted camera inserted through the rectum and into the colon. Unlike a sigmoidoscopy, though, it goes further and scans the left colon and the right. The latter is notoriously hard to navigate and the site of many cancerous growths that go unnoticed.
While getting a colonoscopy is pretty darn low on the pleasantry scale, it’s also one of the most effective tools doctors have to look for and prevent colon cancer. Yet the new DNA blood test may be even more accurate than this often-favored method of colon cancer screening.
The USPST’s current guidelines are that adults between 50-75 should screen for colon cancer with either:
Stool Test – Yearly
Combined Sigmoidoscopy and Stool Test – Sigmoidoscopy every 5 years with a stool test every 3 years.
Colonoscopy – Every 10 years. Note that colonoscopy is sometimes covered by Obamacare.
DNA Blood Testing – The Future of Colon Cancer Screening?
The new DNA blood test is a milestone in colon cancer screening because it’s very accurate and can be done at home. That opens the door for many people who avoid screening for colon cancer because of costs, preparation, and the general idea of having a camera go where the sun don’t shine.
This new method, called the ‘Cologuard Test‘, checks for blood and abnormal DNA in waste. That’s an advantage because some lesions and cancers don’t bleed very much. It was also more likely to detect cancerous polyps in advanced stages; precancerous growths are typically flat in the right colon and can often get missed in a colonoscopy.
To gauge the potential of the Cologuard test, researchers screened nearly 10,000 men and women for colon cancer and precancerous polyps at one of 90 sites across the US and Canada. Each patient was an ‘average’ risk for colon cancer and screened with a colonoscopy, a blood fecal test called FIT and the new DNA Cologuard Test.
Like most blood fecal tests, the Cologuard test required patients collect stool samples and send them to a lab for analysis.
When the study ended, the colonoscopy found 65 new cases of colon cancer and 757 precancerous lesions. The Cologuard test caught 60 of those cancers while the standard blood test picked up 48 – an accuracy rate of 92% for the new DNA test and 74% for the blood test respectively.
Cologuard beat the blood test in other categories too, with a 42% success rate for catching pancreatic lesions vs just 24% for the standard blood test and it was better for precancerous polyps compared to the FIT test. But wasn’t perfect – Cologuard was more likely to falsely detect cancer more than colonoscopy or FIT.
The researchers note Cologuard isn’t meant to replace colonoscopy. Rather, its benefit may be as a supplement to the practice. If it catches something that warrants attention, a colonoscopy should follow.
A Sigmoidoscopy is Better Than Nothing
Even if you’re not keen to do a colonoscopy or home blood test, a sigmoidoscopy is better than no screenings at all. Another study released in August 2014, this one in the Journal of the American Medical Association, found the procedure cut risk of death from colon cancer by just over 25%.
Sigmoidoscopy is less common than colonoscopy, in large part because it’s less comprehensive. Sigmoidoscopy just looks at the lower portion – the left side – of the colon, while colonoscopy is a more thorough exam.
Sigmoidoscopy just looks at the lower portion – the left side – of the colon, while colonoscopy is a more thorough exam.
Still, it’s better than nothing. Sigmoidoscopy often prevents colon cancer because it allows doctors to look for and remove polyps. That’s according to a Norwegian trial, in which researchers gave a one-time sigmoidoscopy to over 20,000 adults between 50 and 64. They compared this group to 78,000 people the same age with no colon cancer screening whatsoever.
Half the sigmoidoscopy group also took a stool test not unlike the FIT test described above.
On the study’s conclusion, the people who had screening were 27% less likely to die of colon cancer over the next decade than folks who did not do the procedure. In other words, sigmoidoscopy is less effective than colonoscopy, but it’s cheaper and less intrusive. If it’s the difference between doing a sigmoidoscopy or not screening, you’d be better off to go for a sigmoidoscopy.
What it All Means
The future of colon cancer screening may belong to procedures like the Cologuard DNA test. Observers of that study note blood tests are getting better by the year. While it’s doubtful they’ll displace colonoscopy as the go-to screening tool, they’ll probably surpass sigmoidoscopy in accuracy and popularity.
It’s not impossible more doctors will encourage patients to get a DNA blood test first and do a colonoscopy if the former turns up something that should be addressed.
While the sigmoidoscopy is still useful, and comes in at a cheaper $150-$300 vs the $1000+ you’d pay for a colonoscopy, it’s getting displaced by improvements in fecal blood stool testing and their ability to analyze DNA abnormalities. Better than a sigmoidoscopy? Probably, yes, and with less of a hassle.
About the only thing you should not do is ignore colon cancer. The illness is now the third-most common cancer on the planet, primarily in developing nations, and affecting more young people than in previous years – in whom it’s often more deadly.
What it all means – get screened for colon cancer. Follow the USPST’s recommended screening guidelines. While not enjoyable, it’s easier than ever to get colon cancer before it turns deadly.