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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?

#61

Post by mgraczyk »

tptacek wrote: post #60
mgraczyk wrote: post #58

Earlier quoted context omitted.

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

Again, you're assuming the only downside of a routine scan is anxiety. No, the real downside is that you'll trigger needless invasive procedures.

How can you trigger an invasive procedure if nobody learns the result of the scan?

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

#62

Post by tptacek »

mgraczyk wrote: post #61
tptacek wrote: post #60

Earlier quoted context omitted.

Again, you're assuming the only downside of a routine scan is anxiety. No, the real downside is that you'll trigger needless invasive procedures.

How can you trigger an invasive procedure if nobody learns the result of the scan?

Obviously, the doctor does. Nobody was ever claiming that the problem with full-body scans was that patients were demanding biopsies!

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

#63

Post by mgraczyk »

tptacek wrote: post #62
mgraczyk wrote: post #61

Earlier quoted context omitted.

How can you trigger an invasive procedure if nobody learns the result of the scan?

Obviously, the doctor does. Nobody was ever claiming that the problem with full-body scans was that patients were demanding biopsies!

Right, the problem in your model is that the doctors do! I am pointing out that this is a problem with the doctors, not the scan.

Scans are a tool, doctors are not allowed to use them rationally because it would be too expensive, so they don't use them. With an ideal doctor, patient outcomes would be better with a scan than without one, but my claim is that doctors are not ideal.

No doctor would order a full body MRI just to throw out the result in 99% of cases, because *it's too costly*

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

#64

Post by somewhereoutth »

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…

No.

When there is low prevalence of a condition, but a non-zero false positive rate of a test, the false positives generated by universal testing can in fact be a net dis-benefit (worry, invasive further procedures, etc) to the patient population as a whole, regardless of cost. This is a well understood statistical phenomenon, and is carefully considered by healthcare systems when advising on testing.

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

#65

Post by tptacek »

mgraczyk wrote: post #63
tptacek wrote: post #62

Earlier quoted context omitted.

Obviously, the doctor does. Nobody was ever claiming that the problem with full-body scans was that patients were demanding biopsies!

Right, the problem in your model is that the doctors do! I am pointing out that this is a problem with the doctors, not the scan. Scans are a tool, doctors are not allowed to use them rationally because it would be too expensive, so they don't use them. With an ideal doctor, patient outcomes would be better with a scan than without one, but my claim is that doctors are not ideal. No doctor would order a full body MRI…

Doctors are not ordering biopsies to salvage the value of a scan they just ordered.

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

#66

Post by mgraczyk »

somewhereoutth wrote: post #64
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…

No. When there is low prevalence of a condition, but a non-zero false positive rate of a test, the false positives generated by universal testing can in fact be a net dis-benefit (worry, invasive further procedures, etc) to the patient population as a whole, regardless of cost. This is a well understood statistical phenomenon, and is carefully considered by healthcare systems when advising on testing.

Read my #2 option, which accounts for that

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

#67

Post by mgraczyk »

tptacek wrote: post #65
mgraczyk wrote: post #63

Earlier quoted context omitted.

Right, the problem in your model is that the doctors do! I am pointing out that this is a problem with the doctors, not the scan. Scans are a tool, doctors are not allowed to use them rationally because it would be too expensive, so they don't use them. With an ideal doctor, patient outcomes would be better with a scan than without one, but my claim is that doctors are not ideal. No doctor would order a full body MRI…

Doctors are not ordering biopsies to salvage the value of a scan they just ordered.

I agree, but they are failing to order scans when the probability of finding anything worth biopsying is low because of cost.

This is so obvious it's crazy, our entire world view is misshaped around saving money.

When you walk into a doctor's office, why do they take your blood pressure and temperature? Why do they look at the back of your throat and listen to you breath?

These are all diagnostic procedures with extremely high false positive rates. The reason doctors do these but do not do MRIs is because MRIs are expensive.

If MRIs were free you would get one automatically every time you go to the doctor.

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

#68

Post by gullywhumper »

sharkweek wrote: post #27
mmaunder wrote: post #13

“ One study in 2020 found that 95% of asymptomatic patients had some type of "abnormal" finding, but just 1.8% of these findings were indeed cancer.” This has been my experience. And I’ve had oncologists echo exactly this. In the words of one: MRIs find too much. The CT and the PET/CT are the gold standards for finding cancer, finding recurrences, and staging cancer. The trouble is the radiation dose. MRI provides ve…

I had a CT scan last year for some stomach issues they wanted to look at. Doctor warned me up front that the odds the images find something that looks weird is high but not to panic because of how many false positives there are when looking inside someone’s body. While I am happy to report they didn’t find anything serious, I do take slight offense to the following at the top of my results: Last name, First name: Unr…

2.5 years in of regular PET scans. At this point, I’m almost humored by what gets flagged as suspicious by the radiologist - usually mosquito bites and stomach bugs (kids in daycare means I’m almost always sick). I have a scan Monday and two weeks ago had a re-excision so there’s a two inch gash healing on my back. This week I got three vaccines. And then tonight my toddler bit me hard enough to draw blood. I had asked the oncologist if it made sense to delay the scan because of the re-excision and he said not to worry because he’d know why there’s inflammation in that area. I’m thinking the bite and the shots will probably get flagged too. I just hope I don’t forget any other maladies or mishaps that might get flagged that I can’t explain.

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

#69

Post by jml78 »

lich_king wrote: post #50
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…

Why is it good for the patient? I think that to claim this, you'd need to show a difference in outcomes. Here, you have a tool with a ~100% false positive rate, so if we start administering it to everyone, it will almost certainly cost lives. Botched biopsies, unnecessary treatments, other complications. Not to mention the huge cost that would divert money from other welfare programs. So you need to show that when it…

I wouldn't argue we should roll this out to everyone. But I am glad it exists. I commented earlier in this topic about how it caught cancer in my wife at the age of 44. She didn't have to go through chemo or radiation treatment because it was caught so early. Surgery removed the whole cancer.

Additionally for me, I have a scan that shows what my body currently has. I had something show up that I did get a scope to check out that was a pancreatic rest. No big deal. Now, if I ever have another MRI and somethings is somewhere else, we have a baseline to compare against. Everything is a risk calculation. When I did my MRI, I also had other procedures done like a heart calcium score.

I will get a little more personal. We didn't do it out of the blue. My wife and I decided we want to live on a sailboat. That was a big purchase for us and boats take a long time to sell. We didn't want to commit to such a purchase then 1 year later find out either of us had cancer then we have the stress of cancer and the stress of trying to sell a boat.

I would never suggest everyone do it, but I am happy we did.

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

#70

Post by tsoukase »

There are two points in MRIs that limit or (better) regulate their use:

* financial cost vs level of care. A full body MRI costs a huge sum but it is the most detailed non-invasive diagnosis we have for any disease that can lead to earlier therapy. Used as a screening method, does it worth to save one patient in tens/hundreds tests performed? You answer, but public health authorities, health insurances and medical societies are negative.

* MRI shows some minor findings that would never cause symptoms and better not be known to the patient due to the stress they bring and cost of ongoing follow up (eg in the brain small meningiomas or angiomas). This might bring more harm than good and limit their net value.

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