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Comment by mgraczyk | Hacker News Reader

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 you have an obviously growing mass that has a probability greater than 95% of being cancerous

Obviously #2 is better for the patient than #1, but #1 is equivalent to never testing if you ignore cost.

So the actual reason we don't have effect frequent scans combined with effective diagnostic techniques is cost, and doctors cope with this reality by saying clearly wrong things about "over diagnosis". It's a local minimum of the payer/provider dynamic that has nothing to do with scans per se.

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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 actually detects something, it saves at least as many lives. And I doubt that's the case.

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.

You are deep in the cope here.

There is no world in which biopsies cause more harm than detecting every cancer at stage 1 prevents.

> Not to mention the huge cost that would divert money from shareholders

Ah, that explains it

I’ll give you a counter example. I had an MRI of my neck for unrelated reasons. It found a thyroid nodule with suspicious characteristics. Incidentally I had had an MRI of the same areaa few years before and it wasn’t there.

So I had a biopsy. Which was equivocal also.

So I had it out which involved removing half my thyroid. Turns out it was a cancer but like the least serious kind, in fact the classification of it as actual cancer has gone back and forth over the years

But my other half of my thyroid couldn’t produce enough thyroid hormone, and now I have to take thyroid replacement the rest of my life to start alive

Also the surgery affected my voice and I sound like RFK jr now.

I clearly suffered some harm, and even after having the thing out, it’s unclear if that was beneficial at all. A large proportion of these kind of tumors quit growing and never do anything bad. But some do. So who knows.

Was the tradeoff worth it?

I don’t think it’s possible to say

Did you read my two options? Do you agree option 2 is better than option 1? If so, then scans are better than no scan

You don't need to show that it's possible to avoid false positives. That's doctors being irrational.

You only need to show that it's possible to build a diagnostic system that's better than no testing, and I have shown that already

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 an unusual place. Or it may be slow-growing prostate cancer that you can live with for another 20 years, and maybe it's the chemotherapy that will do you in. It's really not that clear-cut in medicine.

To give you have another example: let's say that the risk of appendicitis in people who have an appendix is 1%. And the risk in people who had an appendix removed is 0%. Does this justify proactively removing the appendix? No, because the consequences of complications are much higher than the harm you're preventing. The same applies here: detection, even if 100% accurate, doesn't mean anything. You need to show that what you do with the result actually helps.

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 longer make a difference whether you treat it or not. Or it may be that you would have lived another 20 years just fine

This is just wrong for many parts of the body. In your brain? Your lungs? Growing for a year between 3 scans 6 months apart? Extremely unlikely to be benign

> The same applies here: detection, even if 100% accurate, doesn't mean anything. You need to show that what you do with the result actually helps.

This is wrong. If you had a 100% accurate cancer detector, fewer people would die of cancer with no downside

> 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.

> 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 lot of the tumors found by agressive scans are like that, but we don't know yet how much exactly and how to tell one from the other. It's a new question that requires decades-long observations to answer.

> This is wrong. If you had a 100% accurate cancer detector, fewer people would die of cancer with no downside

You're saying it as if detection somehow cures cancer, it doesn't.

> 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.

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.

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

Yes, IF we know the numbers, that's the whole problem. Unprompted full-body MRI scans turn up a completely new probability distribution. We CAN'T know the numbers as of today, it takes decades of controlled studies to get them. (Which is exactly what doctors advocate for)

Even for something as studied as colon cancer it's still controversial whether mass colonoscopies are better than occult blood tests. US sticks to the former, Europe to latter. US have higher rates of polyp removal, higher rates of cancer detection, higher rates of surgeries and ... higher mortality rates than EU. Why this happens is being studied today, there are some early results. What is absolutely clear though is that higher detection rates don't automatically lead to better outcomes, it can easily be the opposite.

Or take something as simple as sunscreen. It's well-known that sun exposure for light-skinned people can cause cancer and sunscreen is advised. A few multi-decade studies have shown that while it indeed eradicates the skin cancer it also shortens the life expectancy by a few years.

Primum non nocere, doctors and scientists are unsure whether sunscreen should be applied at scale and you effectively call for mass biopsies and surgeries.

So if this is true, it seems that we must accept that many people will die of cancer we could have detected and cured with frequent scans, because doing frequent scans will overall cause more harm to people who didn't need treatment. So the overall death/harm rate would be worst with more frequent scans?

Isn't that then just a problem with the scan and diagnosis? With more frequent scans it seems highly unlikely that we wouldn't improve this process and end up in a better place.

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

As if there was an easy, foolproof and precise way to calculate these probabilities. "Just only alter the patient when it is appropriate" he said. You can solve all the world's problems this way, just "always do the right thing". Reality, unfortunately, is more complicated.

What if in reality the doctors can only say if the probability is above 60% or not? What if some doctors are better than others at estimating probabilities? What if estimates are influenced by financial reasons by some entity like the hospital or insurer?

> What if estimates are influenced by financial reasons by some entity like the hospital or insurer?

It's this one

It doesn't matter that some cancers are hard to diagnose. What matters is that some are not hard, especially if you have multiple scans spanning several years

Did you know optometrists now scan your retina during ordinary eyeglasses appointments? They didn't do this in the past because it was too expensive. But optometrists cannot diagnose or treat based on these scans. They refer you to an opthamologist.

Some day your PCP will do the same with MRIs, but only once they are cheap. For now only rich people have this luxury

I don't think this is doctors being captured by the system so much as medicine being cautious about scaling interventions without strong outcome data

Nope, this is cope

Tons of diagnostic interventions have been scaled without strong outcome data. For example many clinics now do fractional exhaled nitric oxide (FeNO) tests because they are safe, fairly cheap, and patients often pay directly out of pocket so they are easy to make money on.

But the evidence for the diagnostic usefulness of this test is extremely low, multiple meta analysis have concluded.

The reason FeNO tests are done but not MRIs is because FeNO tests are $40

"First, do no harm."

Your case #2 doesn't have nearly enough information to say whether it's obviously better for a population of patients. There are a lot of other variables you would need to know:

    - The accuracy of detecting a mass
    - The true distribution of masses in the population
    - The likelihood that of falsely detecting a mass in the same place twice (you seem to implicitly assume that false detections are uncorrelated with each other)
    - The likelihood that a real mass is cancerous (you stipulate that this is 95% in your scenario, but you don't say what other factors are used to determine this - as opposed to just knowing that there's a mass that grew.)
    - The positive effect of treatment in the case of true-positives.
    - The negative effect of treatment or further diagnostics in the case of false-positive.

Saying that doctors are lying about over diagnosis to cope with the fact that diagnostic techniques are too expensive is absurd. They have to actually make decisions in the real world, where your two neat little categories can't be known even if they hypothetically exist.

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