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Most cancer screenings don’t extend life, study finds

cnn.com

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Re: Most cancer screenings don’t extend life, study finds

#31

Post by SpaceManNabs »

pajep wrote: post #22
twoodfin wrote: post #10

I am skeptical of the implied lesson of this analysis—and it is a meta-analysis of other research, not an original study. Just take as given that the analysis is correct, and screening for rare Disease A on net has no effect on life expectancy. Almost no one actually gets Disease A, but everyone is screened for it, and that has some diffuse cost to life expectancy: Screen enough people enough times and someone will d…

what are some cancer screening that one should actively pursue?

Speak with your doctor about this, especially because I am not one, but from what I understand, the ones that you have a family history for, are pre-diposed by environment, the common ones, and the ones caught by usual body checks / tests during check ups. Again, not giving advice but things you can start a conversation with your doctor with.

Re: Most cancer screenings don’t extend life, study finds

#32

Post by hedora »

aydyn wrote: post #20

> explained that if breast cancer caused 3% of all female deaths and screenings reduced these deaths by 35%, that’s a good result on its own. But screenings may change mortality overall by only about 1% This statement makes it clear what's going on. In ML terms: class imbalance. 99.9% of people won't ever get colon cancer, and therefore won't ever benefit from a colonoscopy. It won't make any statistical difference i…

Yes, and if you perform dozens of tests per year on the general population, and take action based on the results, then the probabilities add up pretty rapidly.

Re: Most cancer screenings don’t extend life, study finds

#33

Post by ilya_m »

aydyn wrote: post #20

> explained that if breast cancer caused 3% of all female deaths and screenings reduced these deaths by 35%, that’s a good result on its own. But screenings may change mortality overall by only about 1% This statement makes it clear what's going on. In ML terms: class imbalance. 99.9% of people won't ever get colon cancer, and therefore won't ever benefit from a colonoscopy. It won't make any statistical difference i…

I understand the comment's thesis, but I'd like to see more accurate numbers used where real health outcomes are concerned.

The lifetime risk of being diagnosed with colorectal cancer is ~4%. (With the odds trending higher for the younger generation.) The risk of _death_ from this cancer is ~1%.

Re: Most cancer screenings don’t extend life, study finds

#34

Post by pessimizer »

throwway120385 wrote: post #18
amanaplanacanal wrote: post #8

Earlier quoted context omitted.

It looks like they were comparing a group that got screening vs a group that didn’t get screening. If the group that got screening didn’t live longer than the group that didn’t get screening, that seems like a lot of wasted dollars.

Life expectancy is really only one dimension of "health," and it's probably the most shallow dimension. If I'm quadriplegic and confined to a ventilator but I live to 80, that's the same in this metric as if I'm not paralyzed and able to breathe on my own until I die. What if some people in the group that didn't get screening had fewer high-quality years? It might simply be that the last 5 years of life for people wh…

> Life expectancy is really only one dimension of "health," and it's probably the most shallow dimension. If I'm quadriplegic and confined to a ventilator but I live to 80, that's the same in this metric as if I'm not paralyzed and able to breathe on my own until I die.

Claiming that there are missing elements that could possibly turn the equation in favor of screening is cause for further research and analysis. You can't just claim that they fall in your favor; some diagnostic and exploratory processes due to false positives are painful and/or dangerous in and of themselves.

> What if

"What if" is right. You can't just conjure these people into existence to justify current policies, you have to find them and do the statistics.

Re: Most cancer screenings don’t extend life, study finds

#35

Post by hedora »

kazinator wrote: post #14

> But experts say this doesn’t mean you should cancel that colonoscopy or mammogram appointment. That can only be that these experts disagree with the study, because if it were properly conducted such that its findings are true, then in fact its conclusions do add up to skipping colonoscopies and mammograms. The study is saying that the diagnostic procedures have no effect on outcome. You should not waste time on pro…

The article dismisses a population-wide life expectancy increase of 4 months from one of the screens.

If that's your bar, then most preventative screening is probably not worthwhile.

Re: Most cancer screenings don’t extend life, study finds

#36

Post by pessimizer »

DennisP wrote: post #23
amanaplanacanal wrote: post #8

Earlier quoted context omitted.

It looks like they were comparing a group that got screening vs a group that didn’t get screening. If the group that got screening didn’t live longer than the group that didn’t get screening, that seems like a lot of wasted dollars.

Yes but as someone else mentioned, it's like an insurance policy. Buying insurance doesn't make you richer on average, it makes the insurance company richer. But you aren't guaranteed the average outcome, so it's still rational to get the insurance, to cover the cases where you'd otherwise have a catastrophic loss. As with gambling, it's not just about expected value. You also have to consider risk of ruin.

False positives can be debilitating or fatal.

Re: Most cancer screenings don’t extend life, study finds

#38

Post by dullcrisp »

somenameforme wrote: post #29
twoodfin wrote: post #10

I am skeptical of the implied lesson of this analysis—and it is a meta-analysis of other research, not an original study. Just take as given that the analysis is correct, and screening for rare Disease A on net has no effect on life expectancy. Almost no one actually gets Disease A, but everyone is screened for it, and that has some diffuse cost to life expectancy: Screen enough people enough times and someone will d…

There's an amazing mathematical paradox, maybe even better than the birthday paradox, related to screening for rare diseases, that dramatically changes the formula. Imagine there's some terrible disease affects 1 in 1 million people. And there's a test that's 99% accurate. You go get screened for the disease, and it comes up positive. Oh no! What are the chances that it was a false positive? Intuition would tell you…

Oh no! But what if we run the test a third time?

Re: Most cancer screenings don’t extend life, study finds

#39

Post by NeuroCoder »

pajep wrote: post #22
twoodfin wrote: post #10

I am skeptical of the implied lesson of this analysis—and it is a meta-analysis of other research, not an original study. Just take as given that the analysis is correct, and screening for rare Disease A on net has no effect on life expectancy. Almost no one actually gets Disease A, but everyone is screened for it, and that has some diffuse cost to life expectancy: Screen enough people enough times and someone will d…

what are some cancer screening that one should actively pursue?

The other comment basically got it. Ask doctor particularly with family history. All cancers are better treated if caught earlier but some like colorectal cancer have much less severe outcomes if caught early on (eg removing a large segment of colon vs a small polyp)

Re: Most cancer screenings don’t extend life, study finds

#40

Post by pessimizer »

orblivion wrote: post #11
kccqzy wrote: post #3

This is the pertinent quote: > “Cancer screening was never really designed to increase longevity. Screenings are really designed to decrease premature deaths from cancer.” Explained another way, Dahut said, if a person’s life expectancy at birth was 80, a cancer screening may prevent their premature death at 65, but it wouldn’t necessarily mean they’d live to be 90 instead of the predicted 80. Personally I think this…

I mean, you could interpret that as "most cancer screenings don't extend life, because they come back negative". It's the "not most" case you're testing for in the first place.

Not all positive tests are cancer. In some cases, actual cancers could be a tiny minority of positive tests. The tests themselves are a dangerous tool, and the way we minimize that danger is through statistics.
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