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How often do full-body MRIs find cancer?

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

#211

Post by mvdwoord »

_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 appreciate that, but do wonder, if this is an issue with too much data or how we act on that data. In other words, could there be a future where we do have tons more data, but also use the data in such a way to achieve an overall better outcome for patients?

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

#212

Post by sethev »

mgraczyk wrote: post #29

Doctors here are cognitively captured by a system designed to limit cost (and that's mostly a good thing) But scanning frequently is overwhelmingly good for the patient. The problem is the doctors. Imagine two possibilities. 1. You scan every six months and a doctor reviews your scans but never tells you anything no matter what 2. You scan every six months and a doctor reviews your scans and only tells you results if…

Your case #2 doesn't have nearly enough information to say whether it's obviously better for a population of patients. There are a lot of other variables you would need to know:

    - The accuracy of detecting a mass
    - The true distribution of masses in the population
    - The likelihood that of falsely detecting a mass in the same place twice (you seem to implicitly assume that false detections are uncorrelated with each other)
    - The likelihood that a real mass is cancerous (you stipulate that this is 95% in your scenario, but you don't say what other factors are used to determine this - as opposed to just knowing that there's a mass that grew.)
    - The positive effect of treatment in the case of true-positives.
    - The negative effect of treatment or further diagnostics in the case of false-positive.
Saying that doctors are lying about over diagnosis to cope with the fact that diagnostic techniques are too expensive is absurd. They have to actually make decisions in the real world, where your two neat little categories can't be known even if they hypothetically exist.

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

#213

Post by amanaplanacanal »

cyberax wrote: post #84
tptacek wrote: post #31

Earlier quoted context omitted.

I think you're missing the point. The psychological cost of a conditional-positive result is nonzero, and can be very significant (I speak from a little bit of experience here). But far more importantly: the physiological cost of invasive followups when you eventually trip the threshold of "time to go explore with a scalpel" is very high, and the missing evidence this story is about is whether you can get to that thr…

> Treating MRIs the way we treat blood tests would almost certainly result in huge numbers of needless invasive procedures. Again, _all_ you need to do is to make a follow-up scan in 1-3 months to see if there are any changes. It's a preventative tool, so unless you have other indications, it's almost always safe to wait for a bit. And yes, it requires educating patients that sometimes just waiting and doing a follow…

It's a good thought experiment, but what you really need here is a randomized controlled study to see if your new plan results in better outcomes, before you roll it out to the whole world.

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

#214

Post by kube-system »

mgraczyk wrote: post #58
mmaunder wrote: post #56

Earlier quoted context omitted.

This guy has never heard the term 'scanxiety'. Go ask what it means on a cancer forum. The real OG's are the VHL folks. Bet we have a few here on this thread. Respect.

I have, it's the fault of how medicine is practiced to reduce cost. It's completely avoidable, you can just not tell people their scan results if they have no symptoms and the detection is less than 95% likely to be cancer. This is strictly better than the status quo because the only difference is some people who almost certainly have cancer learn that they have cancer and nothing else changes

> you can just not tell people their scan results if they have no symptoms

This article is about services like Prenuvo, where the entire point of the service is to get the results of elective scan not related to any symptoms.

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

#215

Post by hansvm »

mvdwoord wrote: post #211
_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 appreciate that, but do wonder, if this is an issue with too much data or how we act on that data. In other words, could there be a future where we do have tons more data, but also use the data in such a way to achieve an overall better outcome for patients?

Maybe, but there's a human element that can make things worse too. Take prostate cancer as an example. Most men die with prostate cancer. Most men don't die _from_ prostate cancer. It isn't usually aggressive enough to matter. Most people aren't zen enough to accept that though, so just knowing that you have cancer can add stress to your life with measurably bad health impacts from the resulting hormonal changes (reduced immune function, impaired sleep, increased clotting tendency, slower wound healing, etc).

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

#216

Post by kube-system »

jdthedisciple wrote: post #201

> One study in 2020 found that 95% of asymptomatic patients had some type of "abnormal" finding Call me naïve but why don't we just update our definition of "(ab)normal" then?

People often contain features in their body that look abnormal on an MRI but might not actually be issues. The issue is that an MRI doesn’t give enough information to know otherwise. This is why they are typically not used in a routine exam by mainstream medicine.

It’s like running ‘ls -la’ on a directory to determine if there are any issues with a piece of software. It could show things that are really bad. It could show things that look weird. But it won’t conclusively debug the code.

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

#217

Post by _alternator_ »

mvdwoord wrote: post #211
_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 appreciate that, but do wonder, if this is an issue with too much data or how we act on that data. In other words, could there be a future where we do have tons more data, but also use the data in such a way to achieve an overall better outcome for patients?

Ultimately its a balancing act between what we can know and what we can do about it. If you can’t treat a cancer (or your treatment is not effective, cf the radical mastectomy) then knowing who has it doesn’t help. As technology progresses and more cancers become readily treatable, it will make more sense to do early screening, and potentially full body MRIs.

But right now it is likely to cause a huge waste of time, resources, and yes, human lives to know about every little lump in your body.

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

#218

Post by Apes »

kube-system wrote: post #206
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…

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 diagnosis in any sense of the definition. A doctor does.

Claiming an overdiagnosis defense is essentually implying the medical industry is worse for most than doing nothing.

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

#219

Post by matwood »

uf00lme wrote: post #156
matwood wrote: post #105

Earlier quoted context omitted.

> MRIs are great for certain things like herniated disks in your back. I have had a lot of experience with MRIs on both myself (back and knee [1]) and my dogs with herniated discs. The doctors always make it sound like MRIs are great to confirm what's suspected because of other symptoms like pain, but a point in time MRI alone is not that valuable. Everyone's bodies (including animals!) are surprisingly different ins…

Do you know which MRI you used? Not all are equal. Most MRI are 1.5T powered, and you can’t get fine details until you hit 3T. And there are differences even in the 3T power range. There are higher powered MRI which are mostly only used in research, whilst it is a bit scary thinking about the sheer power of them but a 7T machine doing a full scan of you, would be guaranteed nearly to find anything wrong with you. Whe…

My knee and back was years ago, so probably the 1.5T. No idea on my dogs who have had the more recent MRIs. Their scans are incredibly detailed though, so maybe the 3T?
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