I read with interest your blog today, and then some of your other offerings. I am a rural general surgeon who has done 12,000 colonoscopies in 35 years. My question is how do we know that screening is effective at reducing mortality?
I know that it has been “proven” to reduce mortality in the general public. But this study was done during a time when the public was also simultaneously made aware of the benefits of daily aspirin and began to embrace it (roughly at the same rate and time as screening colonoscopy, 1990 to present). Since it is well established that a simple aspirin each day will lower mortality from colon cancer, how do we know that it was not the aspirin the study participants took that lowered their mortality? I doubt the study design corrected for aspirin.
I sometimes get the feeling that it is all a big hoax perpetrated by people like you and me who profit greatly from screening scoping. I would challenge you to make an estimate of the cost per saved life. My analysis of my own practice and the cost/benefit ratio, is that each saved life costs 5-10 million dollars. While that may be worth it to the saved person, that money may be better spent on care of the needs of many, many other people. Properly spent, it could save more than one life, perhaps?
And while you’re at it, in your blog, explain how the American people spend 5 times more per capita than the rest of the world for health care and get only “pretty good” care, but not the best. I submit that expensive (and therefore, lucrative) ideas like screening colonoscopy are part of the reason for that problem with our health care.
I await your reply…..
-A simple country doctor, with a fully functional conscience
I received this letter last year and wanted to answer it completely and fairly…but like many things, I was never able to find the time! It has been haunting me since then as a challenge unanswered, especially since a large chunk of what I do for a living is colonoscopy. I “believe” in the test because I know its strengths and weaknesses, and that overall it is an excellent procedure that saves countless lives each year. But can I convince our “Simple Country Doctor” friend?
First I will tackle the main question: Does screening colonoscopy prevent death from colon cancer? The answer is a resounding YES! There are many recent, large, well-done studies showing that colonoscopy prevents death from colon cancer. Truth be told, the only randomized, controlled data we have that lower endoscopy prevents colorectal cancer was done using flexible sigmoidoscopy (not colonoscopy), with a clear reduction in mortality from flexible sigmoidoscopy, mainly for left-sided colon cancer. So far, all studies on colonoscopy have been observational in nature, however the methods have been sound and the conclusions have been reproduced by many other researchers, all lending to the credibility of the data.
Here are a few highlights:
A US 2013 cohort study followed 88,902 people over 22 years and found that colonoscopy dramatically decreased risk of death from colorectal cancer.
An international 2014 meta-analysis of both flexible sigmoidoscopy and screening colonoscopy showed that screening colonoscopy was associated with a 68% reduction in colon cancer mortality.
An international 2016 meta-analysis of a total of 1.49 million patients showed that colonoscopy was associated with a 61% reduction in death from colorectal cancer.
And if this is not convincing enough of the mortality reduction due to screening colonoscopy, the first randomized, controlled trial of screening colonoscopy is currently underway with results being expected in the 2020s!
So how does colonoscopy prevent colon cancer from occurring (and therefore reduce the risk of death from colon cancer)? Well, any regular reader here knows that removing precancerous polyps is the key to preventing colon cancer from happening. Polyps grow relatively slowly, offering ample time to stop colon cancer in its tracks. A follow up to the National Polyp Study looked at patients for up to 23 years after colonoscopic polypectomy, and found a 53% reduction in death from colorectal cancer in patients who had polyps removed by colonoscopy performed in the 1980-1990 period. This is pretty strong evidence that removing polyps and engaging in appropriate surveillance colonoscopy prevents colon cancer, with a protective effect that lasts for many years.
The author of the above letter was also concerned with aspirin/NSAID use somehow skewing the study results, citing the known reduction in colon cancer development just by taking aspirin every day. I have covered this in the past, and encourage you to read about the protective effect of aspirin on colon cancer here. However, if what the Country Doctor states is true, if the general public knew all about the beneficial effects of aspirin/NSAIDs on colon polyps and cancer, wouldn’t patients on both sides of these studies be just as likely to be taking aspirin or NSAIDs? Or are the health-savvy prophylactic aspirin-takers more likely to seek out screening colonoscopy too, merely due to better health consciousness? Perhaps their diet is better, and they exercise more too? It’s a valid concern at least…as clustering multiple healthy behaviors with seeking out a screening colonoscopy (another healthy behavior) can artificially inflate the protective effect of the procedure.
Well, for my discerning readers, to answer the above question with some certainly, I looked at the fine print in the methods sections in some of the above-cited articles on colon cancer mortality and colonoscopy, and was ecstatic to find that the authors DID in fact control for aspirin and NSAID use, as well as diet, smoking, alcohol use, and multiple other lifestyle factors! So basically, no, aspirin use alone cannot be responsible for the mortality reduction seen in multiple large studies attributed to screening colonoscopy.