How often do full-body MRIs find cancer? • Hacker News Board

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

#171

Post by gjulianm » Sun, Feb 15, 2026, 12:25 PM UTC

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…

> With my change: 95% of people who are shown scans have cancer and are treated earlier. Without my change: many of those 95% die

Why? What happens if the cancer still doesn't respond to treatment even when detected early? Or, to the contrary, if the cancer also responds to treatment when it starts becoming symptomatic?

That's why we have studies to understand if screening is a good practice or not. It's not that clear cut.

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

#172

Post by gjulianm » Sun, Feb 15, 2026, 12:27 PM UTC

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…

> If the test detects cancer that doesn't need treatment, don't treat it!!

How do you know which ones to treat and which ones to leave?

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

#173

Post by gjulianm » Sun, Feb 15, 2026, 12:32 PM UTC

IshKebab wrote: post #157

srdjanr wrote: post #126

Earlier quoted context omitted.

The question is how can you know if it needs treatment or not. I guess you either need to do a biopsy, or check if it's grown after N months (leaving patient scared and anxious during that time). Neither are great if most cases end up not needing treatment.

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 specific signs and symptoms of the prostate cancer results in the same survival rates.

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

#174

Post by gjulianm » Sun, Feb 15, 2026, 12:37 PM UTC

jmward01 wrote: post #11

Maybe the right answer isn't to do a biopsy, but to monitor the area with follow-up scans? It seems like that addresses much of the harm that a false positive can cause (invasive biopsy leading to complications) while maintaining most of the gains (still very early detection).

> Maybe the right answer isn't to do a biopsy, but to monitor the area with follow-up scans?

Doctors have already thought of this. Several issues with it:

* Monitoring still causes anxiety and mental health issues which come with real effects on patient's quality of life. It's not "harmless".

* Unclear when to monitor and when to treat. It's also really hard to get enough data to characterize these early unspecific findings enough to get confidence on what to do.

* Monitoring via MRI might be just as useful as monitoring via symptoms or any other "passive" methods that do not require a previous scan.

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

#175

Post by IshKebab » Sun, Feb 15, 2026, 12:52 PM UTC

gjulianm wrote: post #172

IshKebab wrote: post #115

Earlier quoted context omitted.

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…

> If the test detects cancer that doesn't need treatment, don't treat it!! How do you know which ones to treat and which ones to leave?

When the result is above a chosen threshold (which may depend on other factors like family history etc.).

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

#176

Post by bell-cot » Sun, Feb 15, 2026, 1:05 PM UTC

rustyhancock wrote: post #53

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…

It's not that MRIs suck at cancer. They provide fantastic structural and functional data. The problem is the specificity of the results and the prior. A full body MRI by definition will provide detailed views of areas where the pretest probability for cancer is negligible. That means even a specific test would result in a high risk of false positives. As a counter point, MRS means that you can now MRI someone's prost…

> Lets say someone has lower urinary tract symptoms. And is 60 years old. An MRI could visualize as well as ...

Not a doctor - but maybe start with some quick & cheap tests of their blood & urine, polite questions about their sexual partners, and possibly an ultrasound peek at things?

At least in America, high-tech scans are treated as a cash cow. And cheap & reasonable tests, if done, are merely an afterthought - after the patient has been milked for all the scan-bucks that their insurance will pay out.

Source: Bitter personal experience.

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

#177

Post by expedition32 » Sun, Feb 15, 2026, 1:05 PM UTC

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…

Not just cost also time. When I had my scan it took 45 minutes and two trained nurses.

Ofcourse in America poor people don't have access to healthcare so it's a lot easier. But in a universal healthcare system everything has to be rationed.

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

#178

Post by codethief » Sun, Feb 15, 2026, 1:12 PM UTC

ErroneousBosh wrote: post #124

rembal wrote: post #15

Earlier quoted context omitted.

Anecdotal evidence to confirm: I had two false alarms from an unrelated MRI scan, and beside wasting a lot of time on diagnosing them - it was also extremely stressful. My father is a part of "full body PET scan every 3 years" program as part of post - cancer treatment, and it worked twice: early detected lung and prostate tumors, both removed.

> My father is a part of "full body PET scan every 3 years" program as part of post - cancer treatment, and it worked twice: early detected lung and prostate tumors, both removed. My mum gets scanned a little more frequently than that, following treatment for an inoperable tumour in her lung around five years ago. During treatment she was getting scanned every three months or so, and it was remarkable watching this t…

> in Scotland where we have (possibly as a result of the weirdly high levels of cancer)

Interesting, I had no idea and just looked this up[0]:

> Scotland had the highest overall incidence (446 for men and 379 for women per 100 000), and Wales had the second highest rate (450 and 366 per 100 000), compared with 394 and 338 per 100 000 in England and 394 and 345 per 100 000 in Northern Ireland.

This would make Scotland rank 3rd in the table on https://en.wikipedia.org/wiki/List_of_countries_by_cancer_ra... .

PS: Glad to hear your mom is doing well!

[0]: https://pmc.ncbi.nlm.nih.gov/articles/PMC1939786/

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

#179

Post by codethief » Sun, Feb 15, 2026, 1:24 PM UTC

jml78 wrote: post #5

lucb1e wrote: post #2

Answering the question in the title... > 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 a bit less than 1.8% of the time in this study > Prenuvo's recent Polaris Study followed 1,011 patients for at least one year following a whole-body MRI scan. Of these patients, 41 had biopsies. More than half of the 41 were diag…

Yep, I have experience with both. It found cancer for my wife and she was able to treat it immediately. Fully recovered. It found a weird spot on me that turned out to a pancreatic rest. The only reason we did the scans were because we were making a significant life decision that we didn’t want to have to backtrack if either got diagnosed with cancer within a year . We knew nothing was guaranteed but we wanted to do…

> The only reason we did the scans were because we were making a significant life decision that we didn’t want to have to backtrack if either got diagnosed with cancer within a year .

Interesting. If it's not too personal, would you mind elaborating on the kind of life decision you were making?

I have never heard of anyone getting checked up for cancer before they make an important life decision. I mean won't a cancer diagnosis disrupt your life anyway?

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

#180

Post by TacticalCoder » Sun, Feb 15, 2026, 1:26 PM UTC

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…

> ... 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.

And if there's one thing where AI models really do already excel at it's classifying and noticing patterns.

Many dermatologists (not all of them yet, at least not in the EU), for example already have software classifiers using pictures of one's skin and helping guide diagnosis. I've lots of moles/nevi and freckles on my skin: I'm one of those Gen X kids raised by parents that had no idea that sun exposure and sunburns was a bad thing so I regularly get warning shots and my body, especially my back, if full of scars for for my entire life dermatologists have regularly removed concerning little buggers and sent them to the lab for further analysis.

Nowadays my dermatologist is helped in her classification by hardware/software.

I don't see why that wouldn't be the way forward for full scan MRI: they'll begin to be more and more hooked up to AI classifiers.

It always takes time: it's not as if the tech comes out and in 48 hours every hospital/physician is equipped with it.

It's literally the future is here (classifiers helping dermatologists find concerning nevi), just not evenly distributed (many dermatologists still don't have access to these latest machines).