Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death • Hacker News Board

Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

#201

Post by JamesBarney » Tue, Oct 11, 2022, 4:55 PM UTC

pbourke wrote: post #184

JamesBarney wrote: post #20

Earlier quoted context omitted.

The study results are "colonoscopies do not lead to a reduction in colon cancer mortality". Reporting that isn't misleading that's what the study says. Basically in the treated group of 1103 of every 10,000 people died. And in the control group 1104 of every 10,000 people died. So to summarize the study. Inviting someone to a colonoscopy reduces their risk of getting colon cancer by 22 basis points. Their risk of dyi…

> The study results are "colonoscopies do not lead to a reduction in colon cancer mortality". Reporting that isn't misleading that's what the study says. The measured intervention was not the colonoscopy, it was the invitation to screen. Only 42% of invited patients actually got a colonoscopy. This is far more persuasive to me: > "When the investigators compared just the 42% of participants in the invited group who a…

The problem is whether or not they chose to get a colonoscopy is a confounding variable which inflates the value of the colonoscopy when some of the results are driven by other attributes.

Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

#202

Post by uslic001 » Tue, Oct 11, 2022, 5:21 PM UTC

I would suggest reading the editorial also. Study has major limitations. From the doctor who wrote the editorial on Facebook Dr Jason Dominitz: "I'm honored to have been invited to write an editorial for the NEJM about the landmark NordICC study comparing screening colonoscopy to usual care (no screening) in Norway, Poland and Sweden. The NordICC results were somewhat disappointing in that colonoscopy only reduced colorectal cancer incidence by 18% at 10 years, with no significant mortality benefit. But only 42% of individuals who were invited to have a colonoscopy followed through. For those that did have colonoscopy, mortality was reduced by 50%. This study highlights the importance of adherence with screening. Also, we know that colonoscopy quality is variable and 29% of the endoscopists were not meeting quality benchmarks for polyp detection. So if you are getting a colonoscopy, ask your doctor what their "ADR" (adenoma detection rate) is. If they don't know, find another doctor to do your colonoscopy. The ADR should be well over 25% and, ideally, over 40%. " https://www.nejm.org/doi/full/10.1056/NEJMe2211595 https://www.nejm.org/doi/full/10.1056/NEJMoa2208375...

Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

#203

Post by uslic001 » Tue, Oct 11, 2022, 5:46 PM UTC

Supermancho wrote: post #155

JamesBarney wrote: post #8

Earlier quoted context omitted.

The gold standard is the invitation. Imagine a study where you try to get one group of people to exercise, and you leave the other alone as a control group. Imagine you find that everyone who actually does the exercise lives much longer. This might be due to the exercise, or it could be that exercise doesn't work but healthier more responsible people followed through with the exercise. And the being healthier and mor…

> The gold standard is the invitation. I'm not sure what gold standard you are referring to (or the article or the paper - https://www.nejm.org/doi/full/10.1056/NEJMoa2208375 ). Double blind studies require there to be data. An invitation doesn't speak to the effects of Colonoscopy screening at all, while simultaneously adding a confounding variable about participation. The data is about the effects of offering scree…

They used intention to treat in the analysis so it included everyone invited to get a colonoscopy but only 42% got the exam. So 58% did not even get the colonoscopy. It is impossible to say what colonoscopy does or does not prevent when the majority of people in the intervention arm of the study did not get the intervention.

Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

#204

Post by dahart » Tue, Oct 11, 2022, 6:54 PM UTC

timr wrote: post #200

dahart wrote: post #194

Earlier quoted context omitted.

> No reasonable person would get one absent demonstrated benefit. But if we insist on measuring demonstrated benefit by factoring in participation rates, then it’s a catch-22. What if given a prior distribution of 100% opt-in, colonoscopies are effective? And you ignored my question about what if we made colonoscopies more convenient, less intrusive and time consuming, which is becoming possible with new tech. These…

> What if given a prior distribution of 100% opt-in, colonoscopies are effective? That is what the "per-protocol" analysis in this RCT estimates. They considered only those people who had a colonoscopy. This completely breaks randomization and is subject to investigator bias, but at least it gives you an idea of the best you could possibly do if you lived in a world where everyone was forced to get one. And that is:…

> a drop of 0.15% in colo-rectal death.

Where’s that coming from? I didn’t read the paper yet, but the article says: “A secondary analysis also offers another silver lining, Gupta said. When the investigators compared just the 42% of participants in the invited group who actually showed up for a colonoscopy to the control group, they saw about a 30% reduction in colon cancer risk and a 50% reduction in colon cancer death.“

> This completely breaks randomization and is subject to investigator bias

Yes, true. I agree with you. This is important when asking the question “how effective is recommending screenings”. But, voluntary opt-in also breaks randomization, and is subject to patient bias.

> you’d need to test 667 people to save one life. That’s a lot of pain for very little gain

Assuming that’s accurate (the article appears to disagree), I’d still be very hard-pressed to agree with this conclusion. Why is a once or twice a decade doctor’s visit spread out over many people amounting to enough pain to let someone die? How much is a life worth? Is the colonoscopy really so bad that you’re willing to risk a greater than one in a thousand chance of dying? That risk is comparable to many extreme sports.

The problem with this kind of sum up the cost and make it look large is that you didn’t do this for anything else and compare it for reference, which makes this framing prone to cognitive bias. We spend billions and have laws for keeping drivers safe, for example. You could make it look insane by adding up the billions of dollars and people-years people spent bucking and unbuckling seatbelts, but the truth is that it’s a teeny inconvenience per person for a sizeable gain in safety and reduction in the accumulated secondary costs of accidental death.

Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death

#205

Post by donohoe » Mon, Oct 17, 2022, 3:13 PM UTC

droopyEyelids wrote: post #137

donohoe wrote: post #109

I personally advise everyone to get a colonoscopy. I personally know 4 people who had the procedure and cancer was detected. Some further along than others. All still living. Colonoscopy is one of the few procedures that as they screen they can also take action.

Your comment is an example of the statistical/scientific misunderstandings that lead to 'overdiagnosis' https://www.cancer.gov/publications/dictionaries/cancer-term... Not all cancer is the same. Every person will have some amount of cancer as they get older. Some of the cancer will not be aggressive or disruptive enough to cause a problem before the person dies of another old-age related infirmary. Treating cancer i…

I take your point, but 2 of the people I refer to had serious stage of cancer and would have died otherwise.