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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?

#81

Post by Nevermark »

> 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

So that would be 1.71% of people getting a full body MRI catching cancer early.

That seems like an astoundingly good return to me. What does late cancer treatment and lost lives cost? Many times these MRI’s.

If everyone did this, would there be any significant number of late stage cancer discoveries anymore?

Obviously, reducing the cost of false positives is important. But if 1.7% of us have cancer - wow. My guess is that percentage can be tuned up and down by demographics. So maybe there is still an argument against everyone doing it.

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

#82

Post by mgraczyk »

lostlogin wrote: post #80
mgraczyk wrote: post #79

Earlier quoted context omitted.

Seems like their main concern is "substantial downstream healthcare costs"

Yes, and needless biopsy can be a big deal. It’s a great document, I’m an MR tech and we now have something to lean on when we say no to these scans. We can then scan people with problems rather than people with too much money.

Great document? I just read the entire thing, it contains no evidence or justification for their claims.

> We can then scan people with problems rather than people with too much money.

Right, this is what it's really about. MRIs are a scare resource and providers need to manage cost. Fortunately I can afford to pay out of pocket, but I'm just annoyed that doctors are so irrational about this

To be clear, it's up to a doctor whether or not to do a "needless biopsy". That has nothing to do with a scan.

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

#84

Post by cyberax »

tptacek wrote: post #31
cyberax wrote: post #22

Earlier quoted context omitted.

"Worth watching" implies that watching is expensive. It's really not. A full-body MRI scan is about $1k, and it can be even cheaper. So if you have abnormal findings in 10% of patients that merit follow-up scans, you can trivially do a series of 3-4 scans without affecting the overall cost too much. Doctors simply need to get out of the headspace where MRIs are extremely scarce tools of last resort and treat them lik…

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-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").

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

#85

Post by lostlogin »

mgraczyk wrote: post #82
lostlogin wrote: post #80

Earlier quoted context omitted.

Yes, and needless biopsy can be a big deal. It’s a great document, I’m an MR tech and we now have something to lean on when we say no to these scans. We can then scan people with problems rather than people with too much money.

Great document? I just read the entire thing, it contains no evidence or justification for their claims. > We can then scan people with problems rather than people with too much money. Right, this is what it's really about. MRIs are a scare resource and providers need to manage cost. Fortunately I can afford to pay out of pocket, but I'm just annoyed that doctors are so irrational about this To be clear, it's up to a…

… they do it based on the scan result.

Avoiding a biopsy that wasn’t needed is a good thing.

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

#86

Post by mgraczyk »

lostlogin wrote: post #85
mgraczyk wrote: post #82

Earlier quoted context omitted.

Great document? I just read the entire thing, it contains no evidence or justification for their claims. > We can then scan people with problems rather than people with too much money. Right, this is what it's really about. MRIs are a scare resource and providers need to manage cost. Fortunately I can afford to pay out of pocket, but I'm just annoyed that doctors are so irrational about this To be clear, it's up to a…

… they do it based on the scan result. Avoiding a biopsy that wasn’t needed is a good thing.

You're imagining that the doctor is required to act irrationally or against the patient's interest. I understand that they do act this way, but I'm pointing out that they don't have to!

You walk into a doctor's office and meet for the first time.

Case 1. You have 3 full body MRIs taken 6 months apart in hand and give them to your doctor. Nobody has opened or looked at the scans yet.

Case 2. You do not have a scan yet

You are claiming case 1 will lead to worse outcomes in expectation. I claim that's impossible because the doctor can simply do the following: Without opening the scans, email them to the world's best radiologist. Tell that radiologist "only reply if it is nearly certain the patient has an operable cancer with the information available"

Now there are 4 possibilities.

Case 1 without cancer: nothing happens

Case 2 without cancer: nothing happens

Case 1 with cancer: you maybe survive

Case 2 with cancer: you die

The only reasonable objection to this is "that's expensive"

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

#87

Post by [deleted] »

mgraczyk wrote: post #59
lich_king wrote: post #57

Earlier quoted context omitted.

No. To argue for the benefit of the procedure, you need to show a difference in outcomes. Not that it can detect something, even if it could (which whole-body MRIs clearly don't). That the detection improves your chances of survival. If you have an growing mass in your body, then if it's cancer, after a year, it might be too late for treatment. Or it may turn out to be nothing: a benign tumor / cyst / fat deposit in…

The difference in out come is With my change: 95% of people who are shown scans have cancer and are treated earlier. 5% of people do not have cancer and get CT scans. 0.5% of people get useless biopsies Without my change: many of those 95% die, the 0.5% do not get useless biopsies And the beauty of this is you can pick the percentage! > If you have an growing mass in your body, then after a year, it may very well no…

[deleted]

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

#88

Post by jmcgough »

OptionOfT wrote: post #47
sharkweek wrote: post #27

Earlier quoted context omitted.

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…

> I do take slight offense to the following at the top of my results: No offense for me, just confusion. One of the status reports started as follows: > OptionOfT is a very pleasant 36-year-old gentleman 6 weeks status post left anterior total hip arthroplasty done by Dr. _ on _. I asked my wife whether I was particularly friendly (I sometimes fail to adjust my demeanor in certain situations). She said: nah, they wri…

The bar is really low for patient behavior. Tbh I find anyone not screaming at me to be pleasant in comparison.

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

#89

Post by _heimdall »

gullywhumper wrote: post #68
sharkweek wrote: post #27

Earlier quoted context omitted.

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 ask…

How often are they finding actual positive hits on the PET? If its so unreliably with regards to false positives why do you continue to have PET scans done?

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

#90

Post by lostlogin »

mgraczyk wrote: post #86
lostlogin wrote: post #85

Earlier quoted context omitted.

… they do it based on the scan result. Avoiding a biopsy that wasn’t needed is a good thing.

You're imagining that the doctor is required to act irrationally or against the patient's interest. I understand that they do act this way, but I'm pointing out that they don't have to! You walk into a doctor's office and meet for the first time. Case 1. You have 3 full body MRIs taken 6 months apart in hand and give them to your doctor. Nobody has opened or looked at the scans yet. Case 2. You do not have a scan yet…

A whole body MRI is low resolution and thick slices, they are crap.

Instead you could get thin slices at high resolution of a body site that has issues or is suspected to have them. Do that instead.

Whole body MR is 5-8mm thick slices at low in-plane resolution. A whole body scan has about 512 pixels over a 50-60cm field of view. Usually it’s even less pixels than this.

Something like a knee, or brain is 2-3mm slices, and high in-plane resolution. A knee is 512 or even 720 pixels over 14cm. It’s vastly better. The difference is stark.

A liver scan or other abdominal organ is lower resolution than a joint or brain, but unlike whole body MR is scanned in multiple planes with multiple image weighting (t1 in/out/fat sat, diffusion, t2, t2fs, gadolinium contrast). A liver scan has thin slices.

Whole body scans generally do two coronal images (stir and t1) then call it quits.

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