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Most cancer screenings don’t extend life, study finds

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

#121
post #105

Earlier quoted context omitted.

Except breast cancer screening, at least via mammography, doesn't save lives. See, for example: https://thennt.com/nnt/screening-mammography-for-reducing-de...

oh wow. "This is an important, though uncommonly discussed, issue in the translation of evidence from cancer screening trials.1 It is known that overdiagnosis (treatment of cancers that would have been no threat), and high false positive rates (misdiagnosis) lead to medical harms and unnecessary surgeries, chemotherapy, and radiation... ...margin of benefit suggested by the analysis above it seems likely that if ther…

[deleted]

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

#122
I am still disturbed by this though. The alternative I see to "get screenings" is "get no screenings." If you're one of the ones who actually do have an aggressive cancer, and you don't find out about it until it's like Stage Four, then you just definitely die, badly and soon. You, specifically, might have been helped if screened when you had a little baby tumor.

So, while I see the "statistically" part, asking everyone to get zero screenings until you start coughing up blood (or whatever happens when the cancer starts showing very obvious signs)... it just seems weird on the individual level. Nobody knows (nor can they know) if you're the person who would be cured with treatment, or if you're the person whose outcome wouldn't have changed a bit with treatment (for better or for worse). That question matters individually, and while "statistically you're slightly more likely to be in the second group" according to these studies, that doesn't make me feel great about just declining all screenings.

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

#123
post #109

What surprising to me is that sigmoidoscopy shows a benefit but colonoscopy doesn’t. In colonoscopy, the entire colon is examined by using a long flexible tube. In sigmoidoscopy, only the lower portion of the colon is checked, again by using a flexible tube. The things that come to mind is that sigmoidoscopy may be better tolerated by patients or have fewer complications.

Likely that the cancers found by the sigmoid are the ones that reduce life years. Perhaps the cancers that are found and treated higher up the colon would have been found out in other ways or not serious enough? I'm not a doctor, so not sure.

Indeed there are dramatic differences between ascending and descending colon cancers.

They are also dissimilar in their chances of presenting early with symptoms making screening less useful vs those that don't present early.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6089587/

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

#124

Earlier quoted context omitted.

Do you really believe your third point? That most medical interventions for cancer do not prolong life? Or the word necessarily means your argument is null like "not all interventions prolong life". Yeah , we knew that already. It's never 100%.

I'd rather die of cancer than die of chemotherapy.

A friend of mine had a pretty agressive cancer at age 16. He suffered through chemotherapy, a bone marrow transplant, and another round of chemo a year later. I think it sucked pretty bad. I visited him once in hospital, they made me wear a full body suit to prevent any infections.

But that was 20 years ago. He lives a normal life now and has a family. I'm pretty sure chemo was worth it.

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

#125

Breast cancer screens def save lives. Can't speak to all screenings but some def work.

I don't know why you're downvoted. The commenters below are misunderstanding things, the NNT page is old and even then it's being mis-cited. I won't go into it but read the caveats section for the author's own explanation.

Screening mammography unequivocally improves cancer-specific mortality. Making the leap to overall mortality is hard, and even a meta analysis is likely too underpowered given the very low overall mortality to begin with. Recall that the smaller the absolute difference is the larger the study will have to be to detect the difference.

For breast cancer we would probably be talking about something like 10 million patients to be adequately powered to draw any conclusion. The older trials also aren't useful/can't be used because the diagnosis and treatment of breast cancer is dramatically different than it was 10 years ago when BI-RADS was in its nascent stage. Accordingly it's not even possible to conduct such a study as it would be unethical to randomize millions of patients to no screening when we know it has proven benefits.

This also raises the question of which outcome measure matters more? All-cause mortality is a good one but it has both pros and cons. Pros being it captures hidden and misattributed deaths and is the least susceptible to bias. Cons include that it underestimates the impact of diseases that aren't high causes of death (i.e. if the patient population is more likely to die of something else the all-cause mortality won't change).

All of this leads to what are we trying to solve with breast cancer screening? It's unequivocal that a screen detected breast cancer is less advanced (i.e. no systemic therapy required) and is associated with cancer-related mortality benefit. The harms of overdiagnosis have also significantly lessened with modern radiology/histology classifications, biopsy techniques and treatment algorithms. Is cancer-specific mortality good enough? I would argue yes given the significant morbidity with systemic therapy and metastatic disease.

To summarize:

1. Screening mammography has been proven to reduce cancer specific mortality in many studies.

2. The only accurate statement about all-cause mortality is "we don't know" rather than yes/no. None of the studies are powered or controlled enough to draw any conclusions.

3. All-cause mortality may not be the best outcome measure to determine whether an intervention is "saving lives" and certainly is not the only measure to consider when deciding on a screening program.

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

#126
post #105

Breast cancer screens def save lives. Can't speak to all screenings but some def work.

Except breast cancer screening, at least via mammography, doesn't save lives. See, for example: https://thennt.com/nnt/screening-mammography-for-reducing-de...

Read all of the caveats. None of this is still relevant. Cancer-specific mortality is definitely reduced.

There is no study powered enough to draw conclusions on all-cause mortality, which may not be the best measure anyway.

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

#127
post #100

Breast cancer screens def save lives. Can't speak to all screenings but some def work.

Evidence?

It's unequivocal that screening reduces breast-cancer specific mortality. None of the studies are powered enough to draw a positive or negative conclusion for overall mortality. The second last link is an explanation of why this is the case, where we're at and what the implications are.

The last link explains the NCCN rationale and decision making process.

http://www.aapec.org/images/b69a380d-519a-415b-8e8c-8e7f2b02...

https://www.nejm.org/doi/full/10.1056/nejmoa1000727

https://academic.oup.com/jnci/article/106/11/dju261/1496367?...

https://www.bmj.com/content/bmj/352/bmj.h6080.full.pdf

https://jnccn.org/view/journals/jnccn/16/11/article-p1398.xm...

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

#128

Is this study just proving that other things kill you while you're being or after you've been treated for cancer?

Someone else linked to https://thennt.com/nnt/screening-mammography-for-reducing-de...

Quote:

> "Two recent data reviews deserve further mention. The United Kingdom commissioned an independent review after dissenting voices swelled, for the purpose of better informing shared decision making and educational materials about the harms and benefits of screening.6 Unfortunately the review concluded that screening mammography trials were inadequately powered to detect an impact on all-cause mortality, and therefore used breast cancer mortality as a primary outcome. They concluded a 20% reduction and used this in their discussion of harms and benefits. As noted above, cause-specific mortality is both scientifically unstable (conclusion reversal is common when all-cause mortality is considered)7 and disease-centered rather than patient centered (patients would prefer to avoid death altogether). Thus, either screening mammography does not save lives or else we have inadequate data to say whether it does or does not. In neither case can a benefit be scientifically claimed."

> "They concluded a 20% reduction and used this in their discussion of harms and benefits."

We want to do things that will help people. On an individual level, people have the right to make decisions for themselves. At the population level, we should do things that can be proven to be helpful. This leads to decisions that feel heartless - denying people a vaccine during a deadly pandemic while it is being tested; delaying or denying introduction of a new medicine that shows only marginal improvements over an old one.

So their independent review showed benefit by changing the criteria for comparison. We want to help people, and medical interventions feel like helping. Unfortunately, sometimes they can be the equivalent of The Politician's Fallacy: "There was a problem. I did something about the problem. Therefore the problem is fixed"

> "As noted above, cause-specific mortality is both scientifically unstable (conclusion reversal is common when all-cause mortality is considered)7 and disease-centered rather than patient centered (patients would prefer to avoid death altogether)."

People die of /something/. That thing becomes a target to fix; and we deploy resources to fix it. We become emotionally connected to some interventions. (Speaking personally, I'm participating in a bike ride in a few weeks to raise money for breast cancer screenings.) Some of those resources are beneficial, some are not, some may be harmful.

> "Thus, either screening mammography does not save lives or else we have inadequate data to say whether it does or does not. In neither case can a benefit be scientifically claimed."

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

#129

Earlier quoted context omitted.

This is the negative expectation part of most medical screening that most analyses miss. - Medical screenings themselves have iatrogenic effects, - the false positives interventions resulting from screenings have further negative effects and - finally the true positive interventions don't necessarily prolong life. All in all very difficult (confounding) tradeoffs that are impossible to quantify and understand especia…

Do you really believe your third point? That most medical interventions for cancer do not prolong life? Or the word necessarily means your argument is null like "not all interventions prolong life". Yeah , we knew that already. It's never 100%.

> most medical interventions for cancer do not prolong life

Specifically, medical interventions for cancer AS A RESULT of some types of screening do not prolong life.

Medical interventions for symptomatic cancer, and some types of screening, certainly do prolong life, and quality of life.

There are so many confounding factors in this it's hard to do something like a pareto breakdown, but it would certainly be interesting to see.

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

#130
post #128

Is this study just proving that other things kill you while you're being or after you've been treated for cancer?

Someone else linked to https://thennt.com/nnt/screening-mammography-for-reducing-de... Quote: > "Two recent data reviews deserve further mention. The United Kingdom commissioned an independent review after dissenting voices swelled, for the purpose of better informing shared decision making and educational materials about the harms and benefits of screening.6 Unfortunately the review concluded that screening mammogra…

so this is almost like a Goodhart's Law problem
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