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

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

#31

Post by jvanderbot »

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…

Well, to be fair, the overall risk of death did not seem to be lower for the invited group. The risk was 11.04 vs 11.03 for those with invited colonoscopy, with fairly large confidence interval on the control group.

But the risk of colon cancer did decrease, with a risk reduction of 18%.

Maybe they just didn't track long enough to tease out a bigger risk reduction in overall mortality, or maybe colon cancer is associated with other risk factors for mortality (like age).

Why someone would latch onto one result and not the other is probably just "blow the lid off" style reporting.

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

#32

Post by em500 »

kmonsen wrote: post #21
rob74 wrote: post #18

Earlier quoted context omitted.

Or it could be that the people that are not necessarily healthier, but have a history of cancer in their family, may be more likely to respond to a colonoscopy invitation? One way or the other, this is all just guesswork...

I feel this is a really reasonable take. This study doesn’t say anything bad about colonoscopy, it says that it is possible the effects are not only due to the colonoscopy so it is probably between 0 and claimed effect effective. Can’t really say where in the range from the study.

Yup.

The study answers a question from health policy makers: Should we invite everyone (in some age group) for a colonoscopy? Based on this study, probably not.

It does not answer questions from individuals: Should I get a colonoscopy? If you have some good reason (symptoms, doctor advice, family history), probably yes (based on other studies, not this one).

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

#33

Post by gwd »

groceryheist wrote: post #5

Sensationalist title to a good news story: there was no intent-to-treat effect, but a low conversion rate. The ETT is a pretty impressive 50% mortality reduction. Also study is limited by a short 10 year follow-up period but there will be a 15 year follow up. So I'll still get my colonoscopy, thanks

Right, so to properly isolate the effect of the colonoscopy on mortality, we need to do a randomized trial with just people like you -- people who would definitely get a colonoscopy if invited -- to see what the effect is. Because you're also more likely to act on early warning signs and get a cancer diagnosis in time to treat the cancer rather than die.

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

#34

Post by hef19898 »

jvanderbot wrote: post #31
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…

Well, to be fair, the overall risk of death did not seem to be lower for the invited group. The risk was 11.04 vs 11.03 for those with invited colonoscopy, with fairly large confidence interval on the control group. But the risk of colon cancer did decrease, with a risk reduction of 18%. Maybe they just didn't track long enough to tease out a bigger risk reduction in overall mortality, or maybe colon cancer is associ…

Invited or not, if you don't show up to a colonoscopy you don't get one. Which means the study's data on invitations alone cannot be used to evaluate the effect of colonoscopies. Seems the study does provide data that allows this so, and shows clear differences in cancer rates and survival rates for those that did get colonoscopies.

Argueing about the randomization of these numbers, and the meta-statistical aspects of that, would be funny if the subject wasn't so serious. It is also the same level of discussion you get from people like JBP, meaning it at least misses the point by a mile.

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

#35

Post by sokoloff »

em500 wrote: post #32
kmonsen wrote: post #21

Earlier quoted context omitted.

I feel this is a really reasonable take. This study doesn’t say anything bad about colonoscopy, it says that it is possible the effects are not only due to the colonoscopy so it is probably between 0 and claimed effect effective. Can’t really say where in the range from the study.

Yup. The study answers a question from health policy makers: Should we invite everyone (in some age group) for a colonoscopy? Based on this study, probably not. It does not answer questions from individuals: Should I get a colonoscopy? If you have some good reason (symptoms, doctor advice, family history), probably yes (based on other studies, not this one).

To the extent that there’s a spread in those answers, a third possibility emerges: how can we, as health policy makers, find a way to make the invitations more effective at converting to administered colonoscopies?

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

#36

Post by robertlagrant »

zerocrates wrote: post #16
akvadrako wrote: post #13

Earlier quoted context omitted.

That suggests something strange though – that those who were invited but non-tested were more likely to die of colon cancer than non-invitie non-testers.

I suppose that by refusing to get a colonoscopy even when specifically prompted to do so, you're maybe sorting yourself into a more "unhealthy" group than the general population of non-colonoscopy-havers.

That would make the outcome less surprising.

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

#37

Post by Findecanor »

pazimzadeh wrote: post #25

> If the endoscopist discovers a suspicious polyp, then it’s promptly removed, thus nipping the cancer before it spreads So, kind of like how pruning a plant does not necessarily weaken it.

When the polyp has been nipped, it is gone. If you have a colon with no polyps (left) in it, you should be safe from colon cancer for at least a decade (how long polyps take to develop from mutation into a tumour).

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

#38

Post by thaumasiotes »

hef19898 wrote: post #34
jvanderbot wrote: post #31

Earlier quoted context omitted.

Well, to be fair, the overall risk of death did not seem to be lower for the invited group. The risk was 11.04 vs 11.03 for those with invited colonoscopy, with fairly large confidence interval on the control group. But the risk of colon cancer did decrease, with a risk reduction of 18%. Maybe they just didn't track long enough to tease out a bigger risk reduction in overall mortality, or maybe colon cancer is associ…

Invited or not, if you don't show up to a colonoscopy you don't get one. Which means the study's data on invitations alone cannot be used to evaluate the effect of colonoscopies. Seems the study does provide data that allows this so, and shows clear differences in cancer rates and survival rates for those that did get colonoscopies. Argueing about the randomization of these numbers, and the meta-statistical aspects o…

> Invited or not, if you don't show up to a colonoscopy you don't get one. Which means the study's data on invitations alone cannot be used to evaluate the effect of colonoscopies. Seems the study does provide data that allows this so, and shows clear differences in cancer rates and survival rates for those that did get colonoscopies.

This is not an oversight on the part of the study designers. It's called "intention to treat", and studies are done this way to get past the problem that, when you invite a bunch of people to get colonoscopies (or tell them to comply with any medical procedure), the people who go through with it are statistically very different, in all kinds of ways, from the people who don't. This makes the direct comparison of "received treatment" vs "didn't receive treatment" mostly meaningless.

You're here advocating for everyone to ignore the study and do a direct comparison of "received treatment" vs "didn't receive treatment".

Don't do this.

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

#39

Post by robertlagrant »

gwd wrote: post #33
groceryheist wrote: post #5

Sensationalist title to a good news story: there was no intent-to-treat effect, but a low conversion rate. The ETT is a pretty impressive 50% mortality reduction. Also study is limited by a short 10 year follow-up period but there will be a 15 year follow up. So I'll still get my colonoscopy, thanks

Right, so to properly isolate the effect of the colonoscopy on mortality, we need to do a randomized trial with just people like you -- people who would definitely get a colonoscopy if invited -- to see what the effect is. Because you're also more likely to act on early warning signs and get a cancer diagnosis in time to treat the cancer rather than die.

> Because you're also more likely to act on early warning signs and get a cancer diagnosis in time to treat the cancer rather than die.

This seems to imply we should discount all treatments because people who choose to get treatment are more likely to get better, coincidentally by the same amount as the treatment's efficacy.

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

#40

Post by hef19898 »

thaumasiotes wrote: post #38
hef19898 wrote: post #34

Earlier quoted context omitted.

Invited or not, if you don't show up to a colonoscopy you don't get one. Which means the study's data on invitations alone cannot be used to evaluate the effect of colonoscopies. Seems the study does provide data that allows this so, and shows clear differences in cancer rates and survival rates for those that did get colonoscopies. Argueing about the randomization of these numbers, and the meta-statistical aspects o…

> Invited or not, if you don't show up to a colonoscopy you don't get one. Which means the study's data on invitations alone cannot be used to evaluate the effect of colonoscopies. Seems the study does provide data that allows this so, and shows clear differences in cancer rates and survival rates for those that did get colonoscopies. This is not an oversight on the part of the study designers. It's called "intention…

I am not doing this, I'm saying the study cannot be used to say colonoscopies don't help.
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