[tptacek]

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 threshold with an MRI.

Treating MRIs the way we treat blood tests would almost certainly result in huge numbers of needless invasive procedures.

[cyberax]

> 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-up scan is right. And yes, I also have a personal experience with that (I had an "idiopathic lymphadenopathy", aka "we don't know WTF is going on").

[amanaplanacanal]

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.

[tptacek]

* Doctors and medical researchers keep saying that routine MRIs for non-symptomatic or low-risk patients is a bad idea, because the outcomes are worse than not scanning.

* There's several clear, understandable mechanistic reasons why this would be the case, including simple applications of the base rate fallacy.

* Nevertheless, here we are, nerds arguing we know better than all these people.

[cyberax]

And I don't buy that. EXACTLY this was also said about prostate cancer screening. Word-for-word. "Overdiagnosing", "people are better off not knowing", "psychological burdens", "invasive procedures", etc.

Now we have multiple longitudinal studies of people receiving aggressive screening and the usual standard of care. The aggressive screening group, unsurprisingly, has better outcomes with less mortality.

> * There's several clear, understandable mechanistic reasons why this would be the case, including simple applications of the base rate fallacy.

Yeah. I guess it's time to stop using fire alarms. People are better off not knowing if a building is on fire, and frequent false alarms have a negative effect on psychological well-being.

Just look at the risk of burning to death. Alarms make no sense at all!

> * Nevertheless, here we are, nerds arguing we know better than all these people.

Yes. Absolutely. And I actually have read (I think) all the studies, and came thoroughly unimpressed. They're utterly sloppy with poor statistical analyses.

It's absolutely an indictment of the medical industry that has become so crusty that it can't be bothered to integrate new diagnostic modality. That is the _only_ way to detect multiple lethal cancers while they are still curable.

[tptacek]

You're not engaging with the logic. Stipulate that it is the only way to detect multiple lethal cancers. If you end up harming more people than you help, the intervention is bad. Right now, you're only looking at one half of the balance sheet.

[cyberax]

> You're not engaging with the logic.

Ditto for you.

> Stipulate that it is the only way to detect multiple lethal cancers.

This is trivially true.

> If you end up harming more people than you help, the intervention is bad.

The only pathway through which diagnostic MRIs can feasibly harm people is aggressive follow-up of uncertain findings. And this is almost completely solved by just doing another scan several weeks/months in the future. With corresponding patient education.

This is literally all what was needed in the case of prostate cancer screening: less aggressive biopsies and bias towards observation rather than action. Yet it took _two_ _decades_ to arrive at this point. And some doctors _still_ refuse to order screening tests out of this misplaced idea of "not knowing is better".

And this is not the only time when "geeks knew better". For example, checklists for surgeries are a no-brainer to anyone with an aviation background. Yet they became standard only two decades ago ( https://pmc.ncbi.nlm.nih.gov/articles/PMC6032919/ )! Over rather strong objections from doctors.

[tptacek]

The people arguing against routine MRI scans are the checklist people!

But, look: if you think routine prostate screening is a good idea, I don't have a counterargument. You're right: there's already an emerging discipline of watchful waiting with prostate pathologies.

The argument being made here is about full body MRI scans: doing a dragnet sweep looking for neoplasms anywhere and everywhere. Not the same thing! Similarly: my belief that the EBM people are right about full-body scans doesn't mean I oppose colon cancer screening!

[lostlogin]

This is pretty much what the experts say:

https://www.ranzcr.com/college/document-library/2024-positio...