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
#2[deleted]
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#3> 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.
I’m really confused by this data. First of all, are they testing the efficacy of colonoscopy or the efficacy of inviting people to colonoscopy?
And then how is the former group’s reduction in deaths 50% and the latter group’s is about 0%?
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#4> 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. I’m really confused by this data. First of all, are they testing the efficacy of colonoscopy or the efficacy of inviting people to colonoscopy? And then how is the former group’s…
They're doing an intention to treat analysis, which can be a bit confusing, but statistically makes sense and is the gold standard for clinical trials.
You're basicall saying "our randomization at the beginning of the trial is key to avoid biases, so we can't reassign people from the treatment group to the other group, even if they practically don't get the treatment". The reason is if you allow people to switch, your assignment is no longer random. People who avoid the treatment may have different health properties than the ones who don't.
In essence, you need your trial to be robust and large enough that a few people not getting the treatment don't matter.
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#5Sensationalist 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
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#6> 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. I’m really confused by this data. First of all, are they testing the efficacy of colonoscopy or the efficacy of inviting people to colonoscopy? And then how is the former group’s…
They're doing an intention to treat analysis, which can be a bit confusing, but statistically makes sense and is the gold standard for clinical trials. You're basicall saying "our randomization at the beginning of the trial is key to avoid biases, so we can't reassign people from the treatment group to the other group, even if they practically don't get the treatment". The reason is if you allow people to switch, you…
Thanks. That explanation on avoiding selection bias makes sense, but it seems like the study is saying those who choose to get a colonoscopy (whether invited or not) are 50% less likely to die of colon cancer.
Also I’m not sure if the article mentioned this, but the data seems to imply that the % of people who opted to get a colonoscopy was similar in the invited and control group.
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#7Sensationalist 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
Where are you getting "50% mortality reduction" from? The article says the reduction was zero:
> After 10 years, the researchers found that the participants who were invited to colonoscopy had an 18% reduction in colon cancer risk but were no less likely to die from colon cancer than those who were never invited to screening.
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#8> 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. I’m really confused by this data. First of all, are they testing the efficacy of colonoscopy or the efficacy of inviting people to colonoscopy? And then how is the former group’s…
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 more responsible causes you to live longer not the exercise.
This could also be true for the colonoscopy, that the more responsible/healthier people in the treatment group are more likely to get the colonoscopy and it's very possible responsibility/healthiness are driving the difference in health outcomes instead of the colonoscopy.
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#9Sensationalist 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
Where are you getting "50% mortality reduction" from? The article says the reduction was zero: > After 10 years, the researchers found that the participants who were invited to colonoscopy had an 18% reduction in colon cancer risk but were no less likely to die from colon cancer than those who were never invited to screening.
> 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
Re: Effect of Colonoscopy Screening on Risks of Colorectal Cancer and Related Death
#10> 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. I’m really confused by this data. First of all, are they testing the efficacy of colonoscopy or the efficacy of inviting people to colonoscopy? And then how is the former group’s…
They're doing an intention to treat analysis, which can be a bit confusing, but statistically makes sense and is the gold standard for clinical trials. You're basicall saying "our randomization at the beginning of the trial is key to avoid biases, so we can't reassign people from the treatment group to the other group, even if they practically don't get the treatment". The reason is if you allow people to switch, you…
Then the title is wrong, since colonoscopies actually do increase survival rates (everything would have surprised me a lot as someone who was saved by one), but rather that invitations for colonoscopies don't work. No idea why, but maybe people willing to do one go anyway while those unwilling are very unlikely to follow an invitation. Either way, the title is wrong, misleading and very clickbaity.