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

#141

Post by ravel-bar-foo » Mon, Oct 10, 2022, 2:44 PM UTC

m0llusk wrote: post #83

This is a very complex subject because the sensitivity of tests for colorectal cancer has improved over time and more testing is being done. This makes it appear as if there is a great increase in colorectal cancer when there really isn't. A very interesting related study has become known as "The Norwegian Colorectal Study" found that early testing was a waste of money since only those with a family history of colore…

There have been some really interesting studies which showed that in order to get colorectal cancer you have to accumulate 4-6 deletrious mutations in the same cells. People with genetic predispositions are born with 2-3 of those mutations. That's why we see this age association. (Just remember being fascinated and thought I would add some context.)

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

#142

Post by dahart » Mon, Oct 10, 2022, 2:51 PM UTC

ricardobeat wrote: post #29

em500 wrote: post #27

Several posters have criticized the title of the news article "In gold-standard trial, colonoscopy fails to reduce rate of cancer deaths". The actual study is titled "Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death" [1] The authors conclude that "In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colono…

There is nothing wrong with the title. The study failed to find a reduction in death rate despite lowering the incidence of cancer, and that is the center of the piece. It goes into detail of why this is surprising. The study authors were interviewed and agreed. The reporting actually adds a lot of context that you would never get from a link to a random study. Like, for example, how it is called the “gold standard”…

> The study failed to find a reduction in death rate despite lowering the incidence of cancer

This isn’t true. The secondary analysis shows a reduced death rate.

The problem with the title is that it says “Effect of Colonoscopy Screening”, not “Effect of telling people to get a colonoscopy screening”, where the primary analysis is making conclusions based on the latter.

Maybe this style of title is standard for medical journals, but the argument in this thread is based on the title priming us for what the paper is talking about, and directly leading to confusion.

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

#143

Post by BenoitEssiambre » Mon, Oct 10, 2022, 2:59 PM UTC

timr wrote: post #129

BenoitEssiambre wrote: post #102

Earlier quoted context omitted.

That is incorrect. The title is completely wrong. "Study failed to find a reduction" _does not equal_ "There wasn't a reduction". From the abstract: "The risk of death from colorectal cancer was 0.28% in the invited group and 0.31% in the usual-care group (risk ratio, 0.90; 95% CI, 0.64 to 1.16)" Look at the confidence interval. This study was both consistent with a 36% reduction in deaths or a 16% increase in deaths…

> That is incorrect. The title is completely wrong....Look at the confidence interval. This study was both consistent with a 36% reduction in deaths or a 16% increase in deaths. It's just a really wide range. All we can say about this study is that it didn't gather enough data to identify the size of the effect, not that there wasn't an effect. In a randomized controlled trial you either find a significant difference…

> In a randomized controlled trial you either find a significant difference in your metrics, or you don't. There's no other option.

This is a poor way of thinking about statistics. Whether you reject or not a sharp null hypothesis doesn't give you much information (See for example: https://www.gwern.net/Everything). Failing to reject in particular, can be compatible with a wide range of effects.

>In all cases where you don't find a significant difference, the problem is that the confidence interval is too wide for whatever difference seems to exist.

With enough data, there could totally have been a tight range around no effect or a small effect. This is not what we got here though.

Also note that other variables such as cancer risk came out significant, so while this study doesn't provide much inductive evidence around cancer death, we do get some deductive evidence based on the known link between cancer and death. Not to mention that cancer and cancer treatments are not fun even when they don't kill you.

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

#144

Post by timr » Mon, Oct 10, 2022, 3:01 PM UTC

dahart wrote: post #139

timr wrote: post #128

Earlier quoted context omitted.

There's not confusion. The study did an intention-to-treat analysis, which failed to find a significant result. "Intention to treat" here means that you count everyone in the group that got an invitation to get a colonoscopy, regardless of whether or not they actually did it. Though this sounds counterintuitive, it's the "gold standard" because, if you don't do this, you leave yourself open to bias -- maybe the peopl…

> Though this sounds counterintuitive, it’s the “gold standard” because, if you don’t do this, you leave yourself open to bias Isn’t there just as much chance for bias if the treatment is voluntary? Maybe the people who are more likely to have health issues are less likely to treat them. I think there is a valid question about how effective a colonoscopy is given that you get one, and a separate valid question about…

> Isn’t there just as much chance for bias if the treatment is voluntary?

I'm not quite sure what you're asking here. If you're wondering if voluntary opt-out of colonoscopy carries risk of bias, then I'll say the following: it's an intervention that is painful, intrusive and time consuming. No reasonable person would get one absent demonstrated benefit.

Pick a thing where people are reasonably likely to do it as default behavior (eating chocolate, say), and the intervention is to abstain from doing the thing, then you'd be right to ask that question. I imagine people who voluntarily abstain from chocolate are pretty different in substantial ways than people who have to be coerced to do so. But people who don't get a colonoscopy when not pestered to do so are just...normal.

> I see what you’re saying - the overall effectiveness of our current system may be low because of a low rate of voluntary adoption of the colonoscopy is low, and even a lower accuracy screen could be more effective if more people opt in.

Not quite. I'm saying that this study did the fairest possible test for effectiveness of colonoscopies, and the effect sizes they found were on par with the genetic tests (to be clear: they didn't actually make this comparison in the RCT; I'm extrapolating from other studies.)

The evidence presented here is not that the genetic tests are a "lower accuracy screen", it's that colonoscopies are likely not better than genetic tests. That's very different.

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

#145

Post by doliveira » Mon, Oct 10, 2022, 3:01 PM UTC

denton-scratch wrote: post #52

This is about colonoscopy screening . If you give a fecal sample and it comes up as suspicious, the next step will be a colonoscopy anyway. A colonoscopy is quite unpleasant; you starve for a day, and take an enema. They may sedate you before the procedure. If they don't, then the procedure is quite uncomfortable; not exactly painful, but unpleasant. Incidentally, if they find and remove a polyp, they will plant a ta…

Wow, colonoscopy with no sedation must be extremely awful. Isn't sedation the default anywhere? I remember the papers I had to sign were really serious about advicing sedation.

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

#146

Post by timr » Mon, Oct 10, 2022, 3:14 PM UTC

BenoitEssiambre wrote: post #143

timr wrote: post #129

Earlier quoted context omitted.

> That is incorrect. The title is completely wrong....Look at the confidence interval. This study was both consistent with a 36% reduction in deaths or a 16% increase in deaths. It's just a really wide range. All we can say about this study is that it didn't gather enough data to identify the size of the effect, not that there wasn't an effect. In a randomized controlled trial you either find a significant difference…

> In a randomized controlled trial you either find a significant difference in your metrics, or you don't. There's no other option. This is a poor way of thinking about statistics. Whether you reject or not a sharp null hypothesis doesn't give you much information (See for example: https://www.gwern.net/Everything ). Failing to reject in particular, can be compatible with a wide range of effects. >In all cases where…

> With enough data, there could totally have been a tight range around no effect or a small effect. This is not what we got here though.

What the trial showed was a small effect with a wide uncertainty on a big sample. We cannot distinguish this from zero.

Again, could the observed effect be significant with a larger trial? Sure. But that's always true for a negative result. The objection carries no information.

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

#147

Post by rammy1234 » Mon, Oct 10, 2022, 3:33 PM UTC

Title and end conclusion of the article are contradicting. Last paragraph says, "If you cannot take 2 days off, then you have other options. If you want to take test once in 10 years, Colonoscopy is the king". This means Colonoscopy is still the king if you can take 2 days off from your work ( which I believe most workers should be able to as this is important for one's life ). Not sure how this is beneficial for the readers of this article.

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

#148

Post by pithymaxim » Mon, Oct 10, 2022, 3:52 PM UTC

em500 wrote: post #27

Several posters have criticized the title of the news article "In gold-standard trial, colonoscopy fails to reduce rate of cancer deaths". The actual study is titled "Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death" [1] The authors conclude that "In this randomized trial, the risk of colorectal cancer at 10 years was lower among participants who were invited to undergo screening colono…

I think it's more important to look at all-cause mortality, because treatment can also harm you. In this case it's a fairly tight confidence interval: "The risk of death from any cause was 11.03% in the invited group and 11.04% in the usual-care group (risk ratio, 0.99; 95% CI, 0.96 to 1.04)."

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

#149

Post by jdeibele » Mon, Oct 10, 2022, 3:54 PM UTC

timr wrote: post #144

dahart wrote: post #139

Earlier quoted context omitted.

> Though this sounds counterintuitive, it’s the “gold standard” because, if you don’t do this, you leave yourself open to bias Isn’t there just as much chance for bias if the treatment is voluntary? Maybe the people who are more likely to have health issues are less likely to treat them. I think there is a valid question about how effective a colonoscopy is given that you get one, and a separate valid question about…

> Isn’t there just as much chance for bias if the treatment is voluntary? I'm not quite sure what you're asking here. If you're wondering if voluntary opt-out of colonoscopy carries risk of bias, then I'll say the following: it's an intervention that is painful, intrusive and time consuming. No reasonable person would get one absent demonstrated benefit. Pick a thing where people are reasonably likely to do it as def…

My father died of colon cancer at age 67. I've been getting screened every 5 years, first by sigmoidoscopy and the last couple of times with the full colonoscopy.

With a sigmoidoscopy you're awake and the doctor will show you what they're looking at. I guess that's intrusive but it certainly wasn't painful.

With colonoscopy, you're under anesthesia. It was probably intrusive but since I wasn't conscious, I didn't care. There was no pain when I regained consciousness.

I'd rather do a stool sample by mail or dropping it off at the clinic if it has the same results as the colonoscopy. There's always a risk with general anesthesia.

I don't know if my case is the norm and yours is the exception. I tend to think it is. My dad missed spending time with his grandchildren and it's possible he'd still be around if he'd been examined. So get that colonoscopy.

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

#150

Post by Findecanor » Mon, Oct 10, 2022, 4:00 PM UTC

greedo wrote: post #106

prirun wrote: post #98

Earlier quoted context omitted.

> The problem with the title is that it might lead individuals to believe they shouldn't bother with getting a colonoscopy. You can't conclude that from this study at all. If your doctor recommends you to get one, you probably should. The problem with your doctor's recommendation is that doctors recommend colonoscopy based on age, not whether you have any factors that might indicate colon cancer. I have no cancer of…

No one in my family history going back several generations had colo/rectal cancer. Yet I developed it at age 41. Diet is increasingly viewed as a factor.

Have you got your genes tested? People can have Lynch syndrome and not develop cancer. Colon cancer is also a silent danger in that it can grow for years without any noticeable symptoms.

I got colon cancer at age 35 (despite being a vegetarian, BTW), and it was first then that suspicion was raised that there could be a hereditary component - which was later confirmed by a gene test.