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How often do full-body MRIs find cancer?
121–130 of 290 posts
Re: How often do full-body MRIs find cancer?
#122“ 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…
> The danger of an unnecessary CT/PET is causing cancer
You'd have to be massively overexposed to CT or PET scanning to cause cancer, like in the region of spending months being scanned continuously with it at full beam current.
Re: How often do full-body MRIs find cancer?
#123Earlier quoted context omitted.
> 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 You assume that treating cancer automatically improves the outcome. Treating cancer often kills you, so treating a non-fatal tumor can easily be a bad decision. And a…
> You're saying it as if detection somehow cures cancer, it doesn't. No, I didn't say the detector would cause cancer to be cured. I said fewer people would die with no downsides. If treatment is sometimes harmful then the detector also fixes that, you'd never treat people without cancer
No, the detector doesn't fix that, that problem is not treating people without cancer. The problem is treating people with cancer that won't kill or harm them during their lifetime. In this case even a low risk treatment becomes harmful, let alone cancer treatments.
Re: How often do full-body MRIs find cancer?
#124“ 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…
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 thing go from the size of a tangerine, to actually expanding a bit and looking "fuzzy" once the drugs kicked in, to being the size of a plum, then the size of a grape attached with a little thin thread of tissue, to being a thing the size of a pea. Now there's a tiny ripple of scar tissue that no-one wants to investigate further, because if it's not doing anything let's not poke at it.
There is a roughly pea-sized "thing" on her adrenal gland that was a bit worrying because anything like that is going to get intimately involved with your lymphatic system and then it's going to metastasise like hell. But it neither got bigger nor smaller in the nearly six years since the first scan, so it can't be that important.
This is one of the great things about the NHS, especially here in Scotland where we have (possibly as a result of the weirdly high levels of cancer) some of the best oncology services in the world.
If we'd lived in the US, the insurance companies would have taken one look at an 83-year-old about to become a grandmother and sent her home with a bottle of morphine to die. As it is, she's doing very well and got to see both her grandchildren start school.
Re: How often do full-body MRIs find cancer?
#125Earlier quoted context omitted.
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…
> The danger of an unnecessary CT/PET is causing cancer You'd have to be massively overexposed to CT or PET scanning to cause cancer, like in the region of spending months being scanned continuously with it at full beam current.
Even if you don't agree with linear no threshold models for cancers induced by radiation (I don't think LNT is accurate).
It comes down to the scan and the age.
3 scans for a 1 year old? Strongly associated with cancers later in life. 5 scans of a 50 year old? Less so.
The 1 year old has an 80 year run way to develop cancer, along with cells already set in a state of rapid division, and a less developed immune system.
But the association is quite strong.
https://www.sciencedirect.com/science/article/pii/S0720048X2...
Re: How often do full-body MRIs find cancer?
#126Can 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…
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.
Re: How often do full-body MRIs find cancer?
#127Earlier quoted context omitted.
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…
> The danger of an unnecessary CT/PET is causing cancer You'd have to be massively overexposed to CT or PET scanning to cause cancer, like in the region of spending months being scanned continuously with it at full beam current.
> You'd have to be massively overexposed to CT or PET scanning to cause cancer
The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed.
Re: How often do full-body MRIs find cancer?
#128Earlier 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…
Some RIS systems make semi form reports with ‘Dear thank you for sending to see us for their etc etc.
Then you can just tab from field to field when doing the report.
Re: How often do full-body MRIs find cancer?
#129Arguments 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 your downtime detection system kept producing false negatives, would your solution to be just turn it off? You'd get some better night's sleep, but you'd pay for it when the system really went down and you had no idea.
Re: How often do full-body MRIs find cancer?
#130Can 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…
> Well fix that problem then. If someone puts a smoke detector above a toaster you don't just pull the battery and call it a day.
I think what's happening here is that the smoke detector is indicating the possibility of fire, but the toaster is always being immediately doused in water. Which as we know would cause more damage than good unless there truly was a raging inferno.
The suggestion here seems to be moving the smoke detector to somewhere where there's a higher chance of it ringing means a higher chance of a damaging fire. Which seems quite reasonable.