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How often do full-body MRIs find cancer?

usatoday.com

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Re: How often do full-body MRIs find cancer?

#221

Post by [deleted] »

Apes wrote: post #218
kube-system wrote: post #206

Earlier quoted context omitted.

This isn’t just about false positives. Most people do have things “wrong” with their body, but they are asymptomatic. The human body can and does cope with a certain amount of failure and/or anomaly as a part of normal operation that we otherwise consider healthy. The problem is that this information is often not actionable. An MRI is great at identifying which ways your body doesn’t look like a textbook reference bo…

> An MRI is great at identifying which ways your body doesn’t look like a textbook reference body, but it doesn’t necessarily tell you what those things are or whether they will ever cause you problems. Its the doctors doing this, not the MRI. There's this weird definition switch that always happens with the "overdiagnosis" defense where the information gets blamed for the overdiagnosis. An MRI doesn't provide any di…

[deleted]

Re: How often do full-body MRIs find cancer?

#222

Post by LogicFailsMe »

nayroclade wrote: post #129

Arguments against proactive MRI scanning always seem to have a whiff of status quo bias to them. Yes, right now MRIs are expensive and false positives are common, but if regular scans were widespread, it's likely this result in innovations that would drive down costs, improve accuracy, as well as producing a much larger corpus of data with which to guide diagnosis and reduce false positives. To use a software analogy…

Same logic as not treating the cancer of an 80 year-old as a heuristic rather than looking at the health, genetics, and epigenetics of the individual beyond the chronological age. Whatever happened to "personalized medicine?"

This article sees methodological failure, I see training data. Training data that could ultimately be used to refine low resolution scans into targeted high resolution scans as needed driving down costs and driving up accuracy. We've already demonstrated AI upscaling, what's the blocker to doing the same for MRI?

And finally, who are any of us to tell people what they can do with their money? China has these things down to $70. And they're leaning in hard on improving them. Cue obligatory China cuts corners blah blah blah. Sigh.

Re: How often do full-body MRIs find cancer?

#223

Post by kube-system »

Apes wrote: post #218
kube-system wrote: post #206

Earlier quoted context omitted.

This isn’t just about false positives. Most people do have things “wrong” with their body, but they are asymptomatic. The human body can and does cope with a certain amount of failure and/or anomaly as a part of normal operation that we otherwise consider healthy. The problem is that this information is often not actionable. An MRI is great at identifying which ways your body doesn’t look like a textbook reference bo…

> An MRI is great at identifying which ways your body doesn’t look like a textbook reference body, but it doesn’t necessarily tell you what those things are or whether they will ever cause you problems. Its the doctors doing this, not the MRI. There's this weird definition switch that always happens with the "overdiagnosis" defense where the information gets blamed for the overdiagnosis. An MRI doesn't provide any di…

Yeah, any doctor worth their salt is going to be diagnosing you based off of the MRI results and some other evidence.

But in the scenarios this article is talking about (Prenuvo, et al), these aren’t scans ordered by a doctor, and there is no other evidence. It is just a patient getting some MRI findings of unknown clinical significance dumped in their lap.

The problem isn’t an overdiagnosis by doctors. The problem is that there’s no doctor diagnosing anything in these instances.

Re: How often do full-body MRIs find cancer?

#224

Post by lostlogin »

ErroneousBosh wrote: post #166
lostlogin wrote: post #127

Earlier quoted context omitted.

> You'd have to be massively overexposed to CT or PET scanning to cause cancer The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0…

> 0.126 to 0.63% So, a just-about-measurable increase, if you pick and choose your values carefully? You are not going to die from cancer caused by getting a PET scan. This will not happen. You're going to die of heart disease or as a not-too-distant second in a car accident.

That data is for one scan, ever.

Continuous scanning for months would give a dose many orders of magnitude higher.

Re: How often do full-body MRIs find cancer?

#226

Post by IshKebab »

gjulianm wrote: post #173
IshKebab wrote: post #157

Earlier quoted context omitted.

If the test provides you zero information about whether it needs treating then it was never a useful test. Presumably it's more like "there's a X% chance this needs treatment". In which case you just set reasonable thresholds for X. E.g. if it's 5% you monitor it, 10% you do a biopsy, 70% you operate, etc. This is much more sensible than just not testing at all and letting people die from cancer. > leaving patient sc…

> This is much more sensible than just not testing at all and letting people die from cancer. This is not what happens. You're assuming that if the cancer does not get detected by the screening then it never gets detected. What actually happens is that the test gives information that might actually be redundant and obtainable in less risky way. What the studies are showing is that waiting until there are other, more…

Interesting. Do you have a source for that?

Re: How often do full-body MRIs find cancer?

#227

Post by danw1979 »

_alternator_ wrote: post #208
nayroclade wrote: post #129

Arguments against proactive MRI scanning always seem to have a whiff of status quo bias to them. Yes, right now MRIs are expensive and false positives are common, but if regular scans were widespread, it's likely this result in innovations that would drive down costs, improve accuracy, as well as producing a much larger corpus of data with which to guide diagnosis and reduce false positives. To use a software analogy…

The major reason not to do this is that you often get worse outcomes for patients. Oncology provides a lot of examples where “more knowledge” does not lead to better outcomes. Routine ovarian cancer screening, prostate screens, childhood neuronlastoma screens, and breast cancer screens all have shown that overuse will identify more cancer, but do not lead to better outcomes like reduced mortality. The reasons are com…

I’m married to someone running various prostate cancer studies in the UK. I hear the arguments against screening a lot and the issue really blew up recently in the news here.

The thing is, when researchers talk about “worse outcomes” they’re often comparing survival (or rather lack of) against terrible side-effects.

What this fails entirely to capture is that doing something to increase your odds of survival, damn the consequences, is an individual choice. It shouldn’t be up to a health economist to make that judgement.

Re: How often do full-body MRIs find cancer?

#228

Post by bonsai_spool »

M95D wrote: post #162
bonsai_spool wrote: post #161

Earlier quoted context omitted.

That’s not the correct framing - your assertion first lacks evidence about why we should screen better. In fact, we aren’t improving longevity in many early diagnoses, and may be treating people whose immune system would resolve the cancers. Further, the denominator is asymptomatic people who were able to get MRI’s they didn’t need . That doesn’t tell us anything about the normal world.

If the cancer is vizible in MRI or CT scans, the immune system already failed to "resolve" it and will not do so in the future, at least not without external help.

> If the cancer is vizible in MRI or CT scans, the immune system already failed to "resolve" it and will not do so in the future, at least not without external help.

This is false. A simple google search for spontaneous remission (or honestly anything similar) would show/have shown you this.

Re: How often do full-body MRIs find cancer?

#229

Post by arjie »

IshKebab wrote: post #115
rich_sasha wrote: post #98

Can someone ELI5 why false positives on a MRI are so bad? From a pure Bayesian PoV, you're better off with a noisy additional observation. At worst it doesn't get much weight. At a pragmatic level, can't you say, hey here's something thats probably nothing, let's scan it again in 6 months? Why does an MRI necessarily lead to invasive follow ups? I get that ideally we'd have a crystal ball with 0 type I / type II erro…

I 100% agree. The UK recently recommended to not scan for prostate cancer because it sometimes detects cancers that don't need treatment: https://www.bbc.com/news/articles/cm20169gz44o.amp This seems super dumb to me. If the test detects cancer that doesn't need treatment, don't treat it!! It's still better to know it's there and that you need to monitor it. > Before you know it, you are on the operating table having…

My parents are doctors so I’m very used to giving them all the data and pushing decision making down to them. Almost all of the time there is no action to be taken. But this built a certain habit that I realized is not conducive to medical care in the US.

I once told my wife that it’s better if she just passes all information downstream and then lets the diagnostician do the diagnostics.

During her pregnancy, at antenatal monitoring, when asked the routine questions I encouraged her to mention everything and so she mentioned a slight twinge in her chest (“it’s probably nothing, maybe something I ate”). She was hooked up to the monitors and so on but this was a sudden moment of panic for everyone but us. The nurse called for a doctor, there was an EKG machine brought up, all sorts of honestly nonsensical reaction given the data.

I realized my mistake soon after. There’s the obvious legal consideration, of course, but the real magic lies in the fact that no one gives full information so if someone sends you a signal they assume it’s crossed some threshold to significance. My mistake was in being a non-normative participant here, akin to someone who drives straight on green in a land where a green light means you first let one person turn left before you go.

Anyway, patients are supposed to perform pre-diagnosis in the US. And you’re not supposed to show your doctor things that they will then act on. You should first apply Bayes yourself and then give the info to the doctor here because they won’t use Bayes.

Re: How often do full-body MRIs find cancer?

#230

Post by [deleted] »

danw1979 wrote: post #227
_alternator_ wrote: post #208

Earlier quoted context omitted.

The major reason not to do this is that you often get worse outcomes for patients. Oncology provides a lot of examples where “more knowledge” does not lead to better outcomes. Routine ovarian cancer screening, prostate screens, childhood neuronlastoma screens, and breast cancer screens all have shown that overuse will identify more cancer, but do not lead to better outcomes like reduced mortality. The reasons are com…

I’m married to someone running various prostate cancer studies in the UK. I hear the arguments against screening a lot and the issue really blew up recently in the news here. The thing is, when researchers talk about “worse outcomes” they’re often comparing survival (or rather lack of) against terrible side-effects. What this fails entirely to capture is that doing something to increase your odds of survival, damn th…

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