[em500]

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 colonoscopy than among those who were assigned to no screening. "

I find it generally more useful link to the (abstract) of the original article, rather than second hand news reports. The abstracts are usually pretty accessible for a somewhat technical audience, they're not written for domain experts only. As we see in the discussions here, it's questionable whether the rephrasing from journalists really adds anything.

[1] https://www.nejm.org/doi/full/10.1056/NEJMoa2208375

[ricardobeat]

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” because it’s a 10-year large scale randomized trial, and the doctors running the study are the ones who promoted colonoscopy as a tool to reduce cancer mortality in the first place.

[em500]

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 study answers a question pertaining public health policy (should we invite everyone in some age group for a colonoscopy?). It does not answer any individual health/treatment/screening question. The article's headline and content is problematic because it's easy to confuse the two, and the vast majority of readers will never get involved in public health policy (but will certainly have to make lots of individual health decisions).

[JohnJamesRambo]

I’m so confused though, because based on my reading of it, it seems like the prostate screening thing where yes it might find cancer but no it won’t prevent deaths, so it might be better to just not know/do invasive procedures and treatment for it.

Is that the wrong conclusion to reach from the data?

[bitcurious]

You could think of screening as a bet on anti-cancer drugs getting better over the next N years.

[PaulHoule]

Prostate cancer is different from colon cancer.

In the case of colon cancer detected in a colonoscopy they can snip it out right there without a lot of effort, risk or lost function. Surgery on the prostate is likely to cause all sorts of problems for men.

[hef19898]

And not having surgery for it can mean death. Steve Jobs, even it wasn't prostate cancer, should serve as good example of how not to tackle it. Or at least to show what not tackeling it looks like, because feel free to do what you want, but be aware of the consequences.

[lupire]

Or you could wait for better drugs before getting an invasive screening.

[prirun]

> 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 any kind anywhere in my family tree and they are always on me to get one.

From the article, a doctor who still believes in colonoscopy for everyone: “The first message is that screening saves lives [Ed: against this study's data] and prevents cancer. If we could have a chance to start everyone at age 45, I’d like that."

[vharuck]

>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.

This study is meant to inform the public health policy of asymptomatic screening. They tried to see if there was a benefit in offering screenings to random patients, regardless of medical history. The currently recommended screenings for asymptomatic people were adopted because meta-analyses showed they reduced cancer mortality. In the US, the US Preventive Services Task Force keeps up with new studies and revises their recommendations: https://uspreventiveservicestaskforce.org/uspstf/home.

For people with family history or other risk factors, doctors will follow different screening guidelines or just order tests whenever they think it useful.

[Clent]

The study does not say that coloscopies don't help. The study measures a difference in the study's population. The study does indicate they don't affect outcomes as much as expected. However, their affect is positive.

The study's measured affect has wide errors bars indicating a larger sample size is needed. Subsequent studies could show the affect is more inline with expectations but are unlikely to show less affect.

The question as to whether this will be used to reinforce hesitancy for this procedure; we can already see it in the comment. Logic and reason are not naturally occurring traits. I predict this will be used to move more people into the control group. Going against medical advice is anecdotally meaningful.

[greedo]

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.

[hef19898]

I had it at 26, go figure. My petvtheory is that in orser to get the average age back to 50, you need someone like me for every 80 year old, statistics are a bitch. That also means my children will have screening coloscopies starting age 16.

[Findecanor]

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.

[mooxie]

I have never had cancer of any kind in my family tree, and I had a precancerous polyp found at 38yo.

You should get a colonoscopy. If you are at low risk and look totally healthy after, they'll tell you that you don't need another for a good while and you'll get the benefit of not (often) getting something that you don't think you need and, as a bonus, not die of treatable cancer.

[SoftTalker]

You'll die of something else then. That's the part that so many people seem to overlook.

There is a money-making industry around colonoscopies and mamograms. I'm not saying to disregard medical advice in this regard as for any individual there may be good reasons to have these procedures. However you can't completely discount the financial incentives for the providers.

[CWuestefeld]

doctors recommend colonoscopy based on age, not whether you have any factors that might indicate colon cancer.

That's not completely true. As a Crohn's Disease sufferer, by doctor has been making me get them since I was a teenager. The indications are high for me. For "normal" people, the general wisdom (apparently based on intuition more than any quantitative analysis) has been that the risks catch up with the general population around 50.

[hondo77]

> 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 any kind anywhere in my family tree and they are always on me to get one.

Wrong. They recommend on both. I had no cancer in my family history but then I got colon cancer (no, I hadn't gotten a colonoscopy before--yes, I was an idiot). As a result, all my siblings' (some of whom are still in their 30s) doctors had them get colonoscopies right away. All negative, thank goodness.

Good luck with sticking your head in the sand.

[ldoughty]

> The problem with the title is that it might lead individuals to believe they shouldn't bother with getting a colonoscopy.

That is exactly what I thought it was saying at a glance. If I skimmed the headline and moved on, instead of digging in, it might have contributed to an unconscious bias against the procedure.

[jrochkind1]

Uh... I think it is what it's saying though? I mean, you should probably still get a colonoscopy if recommended by your doctor which it probably will be right now... but the effects of this study may be to change those recommendations down the line, that is what it suggests. (I think it's not the first, but I'm not sure).

[ldoughty]

The summary I read on CNN:

> In this study, about 12,000 people in Sweden, Poland and Norway got colonoscopies. They saw a 31% reduction in their risk of colon cancer and a 50% reduction in their risk of dying from colon cancer compared with people who were not invited to get a colonoscopy.

https://www.cnn.com/2022/10/10/health/colonoscopy-study-q-an...

[imgabe]

Do people really ignore their doctor's advice because they saw a headline? I'm sure there are some examples, but that can't be the norm. Obviously a colonscopy can still be indicated for an individual even if it doesn't help by doing it en masse for everyone. Specific symptoms could indicate a colonoscopy would provide more information and there are a number of other conditions where it would be used besides colon cancer.

I can't realistically see anyone saying "No thanks, doc, I'm not going to get that colonoscopy you recommended, because I saw a headline"

This trend of saying a thing is bad because you can imagine some unbelievably stupid person misinterpreting it and misusing it is getting out of hand. At some point people are responsible for their own decisions.

[hammock]

>The problem with the title is that it might lead individuals to believe they shouldn't bother with getting a colonoscopy.

Dangerous misinformation!! Censor!! I have reported the author, Angus Chen, to his employer.

Or you could just comment...

[darkerside]

You're walking a dangerous path, friend

[BenoitEssiambre]

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. 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.

This is likely because there wasn't that many people who died of colon cancer in any of the groups. This study just didn't track enough people to provide an answer.

[timr]

> 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 your metrics, or you don't. There's no other option. 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. Your argument here is a fallacy (i.e. "you just didn't do a big enough sample!") which is a variant of my personal favorite: "it would have worked if you'd done X, Y or Z!"

There's always another X, Y, or Z. The negative study is always too small for the people who believe in the thing it's testing. As a supporter of some intervention, the onus is therefore on you to prove your claim in a demonstrated scenario, not on everyone else to disprove it in all scenarios. Could it be true that colonoscopies have some significant benefit to mortality smaller than detectable by a 80,000-person RCT? Sure. But that doesn't make the headline wrong.

This study didn't find a mortality benefit. Arguing that there's some theoretical other study that might find a benefit isn't relevant.

[BenoitEssiambre]

> 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.

[timr]

> 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.

[BenoitEssiambre]

>could the observed effect be significant with a larger trial? Sure. But that's always true for a negative result.

Sure, this is true, it's one of the reasons why results being significant or not is not very relevant. At some point you want to move towards whether the effect size is in a clinically relevant range or not.

>The objection carries no information.

Inasmuch as something like a confidence interval provides an idea of the range of the effect size, more data does carry more information. I know it's complicated to do this analysis properly with prediction intervals and such, but you have no choice if you want to be able to make good decisions with your data. A wide range estimate that doesn't allow you to make good clinical decisions is not useful.

For clinical purposes, I would even have been more confortable treating an significant but small effect in support of the "let's not test" scenario, than this wide range where the effect could be large and positive or negative on the other side and we just don't know. Significant doesn't automatically mean "do the test" and vice versa. Effect size matters! A non-significant result because of a wide interval just doesn't tell you much useful information.

[phkahler]

I'm also confused about the "invited" group. Not all of them had the procedure and there is a part talking about lower cancer rates among the subset that actually accepted the invite. It sounds like there is still confusion about how to interpret it.

[timr]

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 people who seek out colonoscopy have some symptom, family history or other reason that leads them to seek out treatment. Maybe the people who get a test get more treatment, and that treatment is harmful in the marginal case. Or just as importantly: maybe the people who don't have the time/inclination to do one would be better served by an alternative test.

Everyone (including GP) is fixating on the magnitude of the primary outcome and squabbling about whether or not colonoscopies help people. But I think the more interesting aspect of this study is that it shows that the genetic tests probably aren't inferior to the invasive, painful, time-consuming rectal exam. If that's true, it's great news!

[dahart]

> 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 how effective telling people to get colonoscopies is. According to the article, this paper answer the second question strongly via “gold standard”, and the first question less strongly via secondary analysis.

Part of the reason it’s counterintuitive here is the title of the article is “effect of colonoscopy screening”, not “effect of a doctor’s invitation to have a colonoscopy screening”. The title more than suggests that we’re comparing the outcomes of actually having the screening to not having one.

> maybe the people who don’t have the time/inclination to do one would be better served by an alternative test.

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.

One problem with drawing a conclusion this way is it ignores the possibility for dramatic changes in either opinion or in procedure of colonoscopies. What if we had the tech to do the colonoscopy at home in private? Would that change the voluntary rate of testing dramatically?

[timr]

> 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.

[2devnull]

The important part of your post, “If that’s true…”

Is it true, or not?

[timr]

To the extent that we can assess it by this single study, yes.

There is no answer to the question you're asking. You're seeking absolute certainty where none can be had. We only know what we know as far as we know it. Always and everywhere.

[ChrisMarshallNY]

"Death rate" != "Cancer Rate."

Cancer is much more treatable, these days.

I had a friend that just underwent seven months of chemo for colorectal cancer. Looks like he'll be fine, but it was Stage IV, when it was discovered. Had a couple of surgeries, and radiation. The chemo was the worst, though. He channeled Uncle Fester, and this was a fairly robust, somewhat overweight chap.

So he would not go in the "death" column, but I guarantee that he would not be one to dismiss the seriousness of the disease (or its treatment).

[jrochkind1]

I guess the question is if the scan makes a difference in intensity of treatment, if people who got a colonoscopy had fewer surgeries or fewer/less radiation. It doesn't say, I think? It's not at all obvious it would.

(In general, one would think people who got the colonoscopy got more treatment -- in this case despite having no lower a death rate -- but perhaps it does not include as much intense treatment).

[ChrisMarshallNY]

In my friend's case, it was Stage IV, before it was found.

That may have had something to do with him not getting a gerbillcam until he started having symptoms.

I will say his treatment wasn't fun, at all, although he'll be OK, in the long run (but chemo never leaves you the same).

[sillystuff]

> chemo never leaves you the same

For the chemo your friend likely experienced, this is especially true.

Colorectal cancer is often treated with the chemo cocktail, FOLFOX. The "OX" stands for oxaliplatin which causes nerve damage-- hearing loss (less than cisplatin, though), peripheral neuropathy, etc. The second half-life, in the body, of oxaliplatin is 535 months (44 years). And, the platinum remains in a reactive form.

I'd love to hear a professional chime in on if there are ways to speed the elimination. E.g., something like extended/extreme fasting (to free oxaliplatin from tissues) + sodium thiosulfate + blood plasma donation, or something?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2559818/

Some choice quotes from the link:

"The first elimination half-life (t1/2) for cisplatin was 5.02 months and the second 37.0 months. For oxaliplatin, these half-lifes were 1.37 and 535 months."

"...it was shown that Pt species in pUF were still present in a reactive form."

Edit: just submitted the above article:

https://news.ycombinator.com/item?id=33154606

[hef19898]

IMHO it is chemo and the fact you very seriously face the prospect of an ugly, and lengthy, death that changes you. You and your loved ones, it affects everyone, I know it does.

Good for your friend to be on the way of recovering!

[refurb]

Yeah, it's pretty complicated.

I'm not that surprised death rates were similar. Colonoscopies will catch pre-cancerous masses like polyps, so I can see the cancer rate being lower.

But if diagnosed with cancer, treatments are quite good for colorectal cancer, so you may not see that much of a difference in death rate on a 10 year horizon.

[eecc]

Well then the title is indeed misleading. It's not the colonoscopy that's failing to reduce cancer death rates, treatments are. Indeed the title should have been: with colon cancer deaths unchanged, screening and pre-malignant treatments are ever more important.

[pessimizer]

This is nonsensical. Any number of things are failing to reduce cancer death rates, including professional football and jelly donuts. This study is about colonoscopies also failing to reduce cancer death rates.

Changing the title to Don't Worry About Colon Cancer Death Rates, Just Continue To Do What You're Told would not have been better or more accurate.

[eecc]

> This is nonsensical.

Can you please keep it civil and avoid devolving into insults? I don't spend my time online to get treated like a fool. Now please restrain yourself from trolling even further and say "well, then don't say foolish things" because I'd flag you.

If you bothered reading the article, a paragraph reads that this particular form of screening did have an impact. Just not as significant as the community thought.

The study is about _one particular form of screening_ that might might have been oversold. Perfectly consistent with the parent observation and my own: screening is significant, curing cancer isn't as easy as avoiding it altogether.

Now, if you have something constructive to add please do so. Otherwise, please shut up and move on to some Reddit sub.

[refurb]

I think that would be editorialized.

What would be more accurate is to say the title is incomplete. Te details matter.

If the claim was "Voluntary colonoscopy screening does not reduce the risk of death over a 10 year period" it would likely be more accurate and at least calls out the "voluntary" nature of the patients examines and the limited time span of the analysis.

No study is ever perfect and everyone has limitations. You usually learn more by investigating the limitations than poking holes in the conclusions.

[dahart]

> 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.

[readthenotes1]

"The study failed to find a reduction in death rate despite lowering the incidence of cancer, and that is the center of the piece"

Maybe you didn't read the article all the way through?

What it found was it merely inviting people to a colonoscopy did not result in less deaths from colon cancer, although it did result in fewer people being treated for it.

However, if you look at the people who actually took a colonoscopy, there was a 50% reduction in deaths from colon cancer.

That's not nothing.

[jvanderbot]

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.

[hef19898]

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.

[ricardobeat]

You have to look at it from the perspective of medical practice.

The hypothesis is that inviting people for a regular check up reduces mortality. If a lot of people don’t take up the offer because the procedure is too invasive, carries some risk, etc. then that is a very relevant variable to take into account. Vs, for example, fecal testing as mentioned in the article. It could have a lower precision, but if uptake is 100% instead of the ~40% for colonoscopy the outcomes could be much better.

[seanmcdirmid]

American health insurance really screws the pooch here. If you go for a colonoscopy without a previous fecal testing, it is a diagnostic procedure that is fully covered by your insurance without triggering deductible and copay. However, if you go for fecal testing first and then they find something suspicious that warrants a colonoscopy, it is no linger considered diagnostic (you have a legitimate problem now) and deductible/copays apply.

So in practice, doctors will tell you to just get the colonoscopy to save (your own) money.

[astura]

You're not really wrong, but you're using the wrong terms which is extremely confusing.

https://www.cancer.org/cancer/colon-rectal-cancer/detection-...

For asymptomatic people without abnormal stool, colon cancer tests are called "screening," never "diagnostic." "Screening" is covered without cost sharing. Colonoscopy, fecal tests, etc.

>But if you have a screening test other than colonoscopy and the result is positive (abnormal), you will need to have a colonoscopy. Some insurers consider this to be a diagnostic (not screening) colonoscopy, so you may have to pay the usual deductible and co-pay.

[seanmcdirmid]

Thanks for the clarification. I didn’t really know the difference in the terms being thrown around, just the oddness in the billing.

[gregw2]

You are complaining about the rare situation where someone gets fecal scanning first (and I agree this leads to perverse incentives)... But here's what the real racket is... American healthcare considers the colonoscopy preventative so the exam is covered... but if they see even a single polyp and decide to cut it off to get checked whether it is benign or not, that is not preventative but is diagnostic and thus is not covered and costs you $$$ in copays.

[astura]

They aren't supposed to do this - See the link I posted on a sibling comment

https://www.cancer.org/cancer/colon-rectal-cancer/detection-...

>Soon after the ACA became law, some insurance companies considered a colonoscopy to no longer be just a ‘screening’ test if a polyp was removed during the procedure. It would then be a ‘diagnostic’ test, and would therefore be subject to co-pays and deductibles. However, the US Department of Health and Human Services has clarified that removal of a polyp is an integral part of a screening colonoscopy, and therefore patients with private insurance should not have to pay out-of-pocket for it (although this does not apply to Medicare, as discussed below).

[cmurf]

That's what my provider told me too. However:

https://www.npr.org/sections/health-shots/2022/05/31/1101861...

[seanmcdirmid]

Huh. I didn’t see that in my exam. They did a biopsy on one polyp, but I wasn’t charged for it.

[dis-sys]

> then that is a very relevant variable to take into account.

but that variable has nothing to do with whether the procedure itself is effective or not.

[bstpierre]

The question in this context is whether it’s an effective public health measure to recommend the procedure to a population: specifically, does it reduce the number of deaths over a given period?

Whether it’s effective on an individual basis is a related, but different, different question.

[darkerside]

Behavioral medicine

[kgwgk]

> 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.

Really?

You cannot simple compare the outcomes for the people who got an invitation AND got the procedure done with the outcomes for the people who didn’t get an invitation.

You need the compare them with the people who didn’t get an invitation BUT would have got the procedure done if they had been invited.

[thaumasiotes]

> 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.

[hef19898]

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

[kgwgk]

It cannot be used to say that the help either, but you wrote “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.”

[hef19898]

I read it that the invite doesn get you differnces, the colonoscopy itsrlf does. And if that isn't statistically a gold standard, randomization and all tgat, I don't care. What the study says, IMHO, is that invoting people doesn't do any good when people don't show up.

Which is an interesting problem, isn't it? Not inviting people might be an option, one that doesn't provide any benefits, except an number of letters not being sent. So I'd say keep the invites, because every single additional person showing up for a screening is a net win. Additional educating efforts will definetly help so, no idea how those can look like so.

[ricardobeat]

You just did it again.

[hef19898]

Whatever

[kwhitefoot]

> people like JBP, meaning it at least misses the point by a mile.

Who?

[hk__2]

> I find it generally more useful link to the (abstract) of the original article, rather than second hand news reports. The abstracts are usually pretty accessible for a somewhat technical audience, they're not written for domain experts only.

If the second-hand news report is well done, it should give you more context on the matter, and so be more useful than the "raw" abstract.

[pithymaxim]

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)."

[hef19898]

That makes so much more sense and would lead to a much better discussion. Any chance the title and linked site can be changed?

It does show quite nicely how one can lie through scientific studies and confuse people.