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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?

#251

Post by pedalpete »

rustyhancock wrote: post #125
ErroneousBosh wrote: post #122

Earlier quoted context omitted.

> 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…

I think the bigger point you are making is that the 50 year old is also more likely to have developed cancer.

Maybe a full body MRI once a decade is fine until your 30s, then once every 5 years until 50, then once ever 2 years beyond 50.

The test should scale with the probability of cancer.

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

#252

Post by alexey-salmin »

mgraczyk wrote: post #238
alexey-salmin wrote: post #123

Earlier quoted context omitted.

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.

Your claim is equivalent to claiming that most cancer treatment is net harmful btw and this is obviously false, especially for cancers detected earlier

Whether treatment is net harmful or not depends on the level of the risk with no treatment. If you apply treatment with 15% chance of severe side effects to a tumor that will kill the patient with 50% chance in the next five years, of course it's net positive. If you apply it to a first-stage cancer that has 10% chance of progressing to the second stage, the very same treatment will be net harmful.

So no, most cancer treatments aren't net harmful now, but they likely will be in a world where your programme is implemented. Even something as "simple" as biopsy has mortality rates far from zero. Applying it at scale may not have the effect you expect. And surgeries and chemo are much worse.

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

#253

Post by gcanyon »

ryan_n wrote: post #189
gcanyon wrote: post #186

Earlier quoted context omitted.

Not because of an MRI, but this happened to me: 1. I had a chest x-ray 2. It showed a small dark patch, and my lungs over-inflate. 3. Erring on the side of caution, doctor ordered a lung biopsy. 4. Lung biopsy is painful, annoying, expensive, and non-zero-risk. 5. Lung biopsy turns up nothing. "Maybe you aspirated some food?" We learn nothing. N=1, but that biopsy should not have happened.

I don’t understand how you’re concluding that the biopsy shouldn’t have happened from that anecdote? Just because a test result is negative doesn’t mean that it shouldn’t have happened. That’s not how practicing medicine works.

Hence the N=1 I started the statement with. If we had a thousand similar situations and it turned out that in, say, 1% of cases there was a lung tumor, then we could debate whether it's worth putting 990 people through a biopsy they don't need so 10 can find out they have a tumor. Maybe that gives us the opportunity to discuss waiting a month and taking another chest x-ray (which has its own negatives) vs. doing an immediate biopsy.

But we don't have 1000 similar cases. As I said, we have 1: mine. And it turned out negative. So 1 person was put through a biopsy they didn't need, and 0 people found out they have a tumor.

Hopefully that makes my point clearer.

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

#254

Post by mgraczyk »

alexey-salmin wrote: post #252
mgraczyk wrote: post #238

Earlier quoted context omitted.

Your claim is equivalent to claiming that most cancer treatment is net harmful btw and this is obviously false, especially for cancers detected earlier

Whether treatment is net harmful or not depends on the level of the risk with no treatment. If you apply treatment with 15% chance of severe side effects to a tumor that will kill the patient with 50% chance in the next five years, of course it's net positive. If you apply it to a first-stage cancer that has 10% chance of progressing to the second stage, the very same treatment will be net harmful. So no, most cancer…

But do you see how crazy that sounds? If we know the numbers, we would just not do the treatment in those cases.

And in reality it's not actually close like this. Early treatment is so overwhelmingly better than it completely dwarfs all considerations of biopsy risk.

Late stage lung cancer has less than half the 5 survival of early stage, and around 50% of lung cancer detection is late stage. That's around 30000 lives you could save every year from just lung cancer.

Let's say you don't protocol for all adults. Typically post CT or PET at most 10% get a biopsy. So let's say we increase the false positives that lead to CT or PET by X% of adults. That's 270M * X additional biopsies. Lung biopsy mortality is under 2%.

So the worst case you need a false positive rate under 5% for this to he net beneficial for lung cancer. That's low but with 3 scans 6 months apart and a good radiologist, it's not unreasonable

I believe I've assumed the worst case for all the quantities. In reality the addition screened people would have much lower CT detection rate than the background population, and biopsy mortality has been decreasing. Plus you can do this for only people above 40 where the benefits are higher

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

#255

Post by xanrah »

Bender wrote: post #200
JackFr wrote: post #160

Earlier quoted context omitted.

But if you’ve never looked at the log before all these WARNINGs might be normal operation. It’s not turning off logging, it’s saying log at ERROR level.

That's a good point. How many people have a baseline MRI from when they were at their healthiest?

And if everyone had scans at their healthiest we would know better

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

#256

Post by ErroneousBosh »

lostlogin wrote: post #225
ErroneousBosh wrote: post #167

Earlier quoted context omitted.

[citation needed]

5% seems a bit high, but we are nearly there. https://www.facs.org/for-medical-professionals/news-publicat...

I think they're reading too much into it.

How are they determining "this cancer was caused by the CT scan" versus "this cancer was caused by the cancer we were originally looking for that was there all along"?

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

#257

Post by hbs18 »

robocat wrote: post #140
mcbain wrote: post #24

Earlier quoted context omitted.

I have multiple scans a year. "Scanxiety" is real.

> Scanxiety Cute written word - even though two words pronounced completely differently at join (an versus añ). Which do you pronounce correctly the scan or the anxiety? [scan]xiety or [sk]anxiety

As a non-native English speaker, pronouncing it scan-xiety (sken-ZAHyetee) feels correct.

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

#258

Post by FuckButtons »

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…

It’s expensive because superconducting magnets cryogenically cooled in liquid helium are expensive to build and run. No amount of demand signal will overcome that reality.

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

#259

Post by mcbain »

robocat wrote: post #140
mcbain wrote: post #24

Earlier quoted context omitted.

I have multiple scans a year. "Scanxiety" is real.

> Scanxiety Cute written word - even though two words pronounced completely differently at join (an versus añ). Which do you pronounce correctly the scan or the anxiety? [scan]xiety or [sk]anxiety

The former. It doesn't quite roll off the tongue, but with my (Australian) accent the difference is minor.

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

#260

Post by OneDeuxTriSeiGo »

gjulianm wrote: post #245
OneDeuxTriSeiGo wrote: post #184

Earlier quoted context omitted.

> Why is it likely? We already have a lot of MRI data. There are already a lot of incidental findings. It might also be an issue of the MRI not being able to produce enough information to discriminate. This is the main reason. Well technically the opposite of the main reason but more or less it's the same. MRIs are extremely high fidelity nowadays and as a result it's really really hard to read an MRI. Every person i…

> That's actually exactly why it's important to have MRIs more frequently to be able to establish baselines and identify trends as they develop. How? How do you establish baselines? How do you build a classification of incidental findings? It's very possible that you'll find a lot of types and not a lot of representatives of each type. And then you have to correlate that to actual clinical results, but the population…

When I say establish baselines what I mean is to establish baselines for the individual.

If you have records of the locations and sizes of various atypical structures and forms throughout the body going back for years and all of a sudden one of them starts changing in size at a rate disproportionate to its history, that's probably cause to dig a little deeper.

It's certainly not "throw more data at the problem". Instead it's about giving the data a time axis with some decent fidelity.

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