5 ms·

This is incredibly wrong. This whole thread is. Cancer testing is not benign. False-positive cancer diagnosis has a >0 mortality rate, because further testing

by smt88 2y ago

This is incredibly wrong. This whole thread is. Cancer testing is not benign. False-positive cancer diagnosis has a >0 mortality rate, because further testing and treatment is potentially fatal. Just a colonoscopy can be fatal, as can a biopsy that requires anesthesia. The medical world weighs these things against each other and determines when the data shows that the risk of mortality from testing is smaller than the risk of cancer.

blackeyeblitzar 2y ago
> The medical world weighs these things against each other and determines when the data shows that the risk of mortality from testing is smaller than the risk of cancer. Let the patient weigh the odds. Especially when they can afford retesting or may be otherwise in good health or whatever. Plus the test’s algorithms can be tuned to provide more or less false positives.
- smt88 2y ago
  > Let the patient weigh the odds. Patients are uninformed and emotional. Part of a doctor's job is to make the best decision for the patient using the information they have. For example, if you tell people that daily aspirin reduces the risk of heart disease, you might get a 25yo with no heart issues starting to take it. But if you look at actual data, all-cause mortality increases for people who have no risk of heart disease if they take daily aspirin, because aspirin can cause fatal internal bleeding. That's the kind of thing doctors know and need to be firm about.
  - blackeyeblitzar 2y ago
    I disagree. Doctors are frequently incompetent, don’t spend enough time with patients to understand them deeply, and are not aware of the latest research or these nuances. But leaving that aside, this is about patient control. Doctors should not be gatekeepers for diagnostics. I don’t even want them to be a gatekeeper for many relatively safe prescriptions, which is clearly a way to increase medical costs.
    - smt88 2y ago
      > Doctors should not be gatekeepers for diagnostics. Doctors mostly aren't gatekeepers for risk-free diagnostics, like a blood test for a vitamin deficiency. Insurance companies are. But for risky tests, doctors have a duty to "do no harm" and can't/shouldn't order something that they know causes an increase in all-cause mortality for their patients. The concept is the same with antibiotics or anything else a patient might ask for without knowing the risks.
      - ethbr1 2y ago
        > Doctors mostly aren't gatekeepers for risk-free diagnostics That's not entirely true. There are more than a few diagnostics in the US that the FDA explicitly discouraged companies from offering without physician referral. E.g. whole genome sequencing several years ago
        smt88 2y ago
        Whole-genome sequencing leads to unnecessary treatment, like mastectomies. It’s not risk-free.
        ethbr1 2y ago
        Whole-genome sequencing gives me more information about my health than I had before. Being ignorant is not risk free.
modzu 2y ago
the obvious answer is additional testing to reduce the likelihood of a false positive -- if additional tests are invasive those tests can be weighed on the balance of risk just the same. i think the real problem is cost, we cant afford/manage to do that correctly currently, which is exactly what improved non invasive tests could enable and disrupt this reactionary approach forever
- smt88 2y ago
  > if additional tests are invasive those tests can be weighed on the balance of risk just the same So let's say you have an extremely safe test. Let's use the "mail your poop to a lab" test for colon cancer as an example. If that test (regardless of its accuracy) comes back with a positive, you're going to do one of two things: A) order a colonoscopy, perhaps with biopsy, to confirm the presence of a malignant tumor; B) start treatment immediately (if you trust the initial test enough). So that brings you back to square one: you shouldn't do the test, regardless of the safety, if the math works out to make it riskier (due to false positives and unnecessary tests/treatment).
  - modzu 2y ago
    i think i agree about "if the math works out" -- but thats the hard question isnt it? isnt the accuracy of the poop test significant? if 2 or 3 poop tests increase our confidence in the result it changes the risk:benefit calculation for the colonoscopy or treatment. thats an easy win. but even if it did not, is the result from the (preventative) poop test less valid data than a patient complaining of pain? so generally speaking i agree we dont want to enable a path to risky procedures based on dubious evidence, but i think overall we are presently operating with a dearth of information (waiting for symptoms) and the math itself improves by having more proactive testing (information) in the first place
derektank 2y ago
I feel like you're missing the point. Yes, false positives have risks. But if blood tests (or in the case of bowel cancer, fecal tests like cologuard) are effective, we can replace more invasive screening options with them. People have historically been encouraged to get colonoscopies once they reach a certain age because, for the general population, the risks of cancer are higher than the risks associated with a colonoscopy above the age of 50. Developing less invasive tests lets us lower that age, catching more cancers, while at the same time making screening safer for people already in the recommended screening window. Also, pancreatic cancer, which is what the original article is about, has no alternate form of screening. Most people only find out they have it once it's already symptomatic, which is usually stage 3 or 4
- jghn 2y ago
  I'd argue that you are the one missing the point. These things are already taken into account via population scale statistics. In most cases, it's at best debatable whether more or less screening leads to an overall better outcome across the entire population aggregate. The argument against more screening is that it can (and the claim is it does) lead to overall worse outcomes in aggregate. For any individual case however, the story may be totally different. What we need are better mechanisms to bin positive results to steer people towards a finer grained course of action. That'd change the math to be more of an overall net benefit.
- smt88 2y ago
  > But if blood tests (or in the case of bowel cancer, fecal tests like cologuard) are effective, we can replace more invasive screening options with them. That is not what I'm arguing against. People in this thread are talking about testing earlier and more often because we have these new tests, not "just" replacing existing tests. The math is very unlikely to work out that we should do that.
  - ethbr1 2y ago
    Howso? Existing solutions vs more widely deployed and frequent blood+fecal tests followed up by existing solutions in the case of a potential positive?
cameronh90 2y ago
The emphasis there is on "further treatment". The test itself is broadly benign (except the general risks associated with phlebotomy and any risk of psychological harm). The issue is that doctors often over-react to adverse results due to the risk of being sued if it did turn out to be a true positive. I have two examples of this. One was during a routine blood test I had a liver enzyme flag up, which was then further investigated non-invasively with ultrasound and it was determined that I might either have moderately developed NAFLD (non-alcoholic fatty liver disease, I'm obese) or very early stage NASH (non-alcoholic steatohepatitis) associated fibrosis. The doctor wanted to perform a liver biopsy to confirm which is obviously an invasive procedure with a 1%-ish risk of complications. My response was to ask how the treatment would differ between diagnoses, and he said in either case the treatment would be the same: lifestyle change. He agreed that from a risk perspective the biopsy was just inviting additional risk for no benefit, but that policy is to recommend the test and if I refuse it I'll need to sign an indemnification document saying I was refusing further diagnostics against medical advice. A few years go by, I've made efforts to improve my lifestyle, lost weight, and now my liver tests are all normal proving it was just NAFLD after all. In another case, I had a suspicious finding in an eye test which (long story short) led to me getting two head CT scans which showed no problems. In hindsight, I think a double dose of brain radiation over a common minor finding with no other symptoms was a crazy over-reaction and I would have refused if I had all the facts, but it could have been a life threatening situation in some ridiculously tiny percentage of cases so it was all rush rush and I didn't have time to weigh it up. Often the correct thing to do may be a combination of further non-invasive testing, repeating the test (possibly after a period of time), and "watchful waiting". Doctors often don't feel comfortable with the level of personal risk that could expose them to, and for good reason. That is the issue, not the test.
- smt88 2y ago
  > The issue is that doctors often over-react to adverse results due to the risk of being sued if it did turn out to be a true positive. Do you think a patient is going to receive a false positive and accept a response from a doctor of, "Oh, might be a false positive. Let's ignore it and not do any more risky testing."? That scenario makes no sense from either perspective. If you get a positive, you do more testing (or skip to treatment). Your examples are well-taken and I understand them, but they don't apply to cancer. When you detect cancer with any test, you immediately do something risky: either a further test that involves risk, or treatment that involves a lot of risk.

by smt88 2y ago

blackeyeblitzar 2y ago

> The medical world weighs these things against each other and determines when the data shows that the risk of mortality from testing is smaller than the risk of cancer. Let the patient weigh the odds. Especially when they can afford retesting or may be otherwise in good health or whatever. Plus the test’s algorithms can be tuned to provide more or less false positives.

smt88 2y ago
> Let the patient weigh the odds. Patients are uninformed and emotional. Part of a doctor's job is to make the best decision for the patient using the information they have. For example, if you tell people that daily aspirin reduces the risk of heart disease, you might get a 25yo with no heart issues starting to take it. But if you look at actual data, all-cause mortality increases for people who have no risk of heart disease if they take daily aspirin, because aspirin can cause fatal internal bleeding. That's the kind of thing doctors know and need to be firm about.
- blackeyeblitzar 2y ago
  I disagree. Doctors are frequently incompetent, don’t spend enough time with patients to understand them deeply, and are not aware of the latest research or these nuances. But leaving that aside, this is about patient control. Doctors should not be gatekeepers for diagnostics. I don’t even want them to be a gatekeeper for many relatively safe prescriptions, which is clearly a way to increase medical costs.
  - smt88 2y ago
    > Doctors should not be gatekeepers for diagnostics. Doctors mostly aren't gatekeepers for risk-free diagnostics, like a blood test for a vitamin deficiency. Insurance companies are. But for risky tests, doctors have a duty to "do no harm" and can't/shouldn't order something that they know causes an increase in all-cause mortality for their patients. The concept is the same with antibiotics or anything else a patient might ask for without knowing the risks.
    - ethbr1 2y ago
      > Doctors mostly aren't gatekeepers for risk-free diagnostics That's not entirely true. There are more than a few diagnostics in the US that the FDA explicitly discouraged companies from offering without physician referral. E.g. whole genome sequencing several years ago
      - smt88 2y ago
        Whole-genome sequencing leads to unnecessary treatment, like mastectomies. It’s not risk-free.
        ethbr1 2y ago
        Whole-genome sequencing gives me more information about my health than I had before. Being ignorant is not risk free.

modzu 2y ago

the obvious answer is additional testing to reduce the likelihood of a false positive -- if additional tests are invasive those tests can be weighed on the balance of risk just the same. i think the real problem is cost, we cant afford/manage to do that correctly currently, which is exactly what improved non invasive tests could enable and disrupt this reactionary approach forever

smt88 2y ago
> if additional tests are invasive those tests can be weighed on the balance of risk just the same So let's say you have an extremely safe test. Let's use the "mail your poop to a lab" test for colon cancer as an example. If that test (regardless of its accuracy) comes back with a positive, you're going to do one of two things: A) order a colonoscopy, perhaps with biopsy, to confirm the presence of a malignant tumor; B) start treatment immediately (if you trust the initial test enough). So that brings you back to square one: you shouldn't do the test, regardless of the safety, if the math works out to make it riskier (due to false positives and unnecessary tests/treatment).
- modzu 2y ago
  i think i agree about "if the math works out" -- but thats the hard question isnt it? isnt the accuracy of the poop test significant? if 2 or 3 poop tests increase our confidence in the result it changes the risk:benefit calculation for the colonoscopy or treatment. thats an easy win. but even if it did not, is the result from the (preventative) poop test less valid data than a patient complaining of pain? so generally speaking i agree we dont want to enable a path to risky procedures based on dubious evidence, but i think overall we are presently operating with a dearth of information (waiting for symptoms) and the math itself improves by having more proactive testing (information) in the first place

derektank 2y ago

I feel like you're missing the point. Yes, false positives have risks. But if blood tests (or in the case of bowel cancer, fecal tests like cologuard) are effective, we can replace more invasive screening options with them. People have historically been encouraged to get colonoscopies once they reach a certain age because, for the general population, the risks of cancer are higher than the risks associated with a colonoscopy above the age of 50. Developing less invasive tests lets us lower that age, catching more cancers, while at the same time making screening safer for people already in the recommended screening window. Also, pancreatic cancer, which is what the original article is about, has no alternate form of screening. Most people only find out they have it once it's already symptomatic, which is usually stage 3 or 4

jghn 2y ago
I'd argue that you are the one missing the point. These things are already taken into account via population scale statistics. In most cases, it's at best debatable whether more or less screening leads to an overall better outcome across the entire population aggregate. The argument against more screening is that it can (and the claim is it does) lead to overall worse outcomes in aggregate. For any individual case however, the story may be totally different. What we need are better mechanisms to bin positive results to steer people towards a finer grained course of action. That'd change the math to be more of an overall net benefit.
smt88 2y ago
> But if blood tests (or in the case of bowel cancer, fecal tests like cologuard) are effective, we can replace more invasive screening options with them. That is not what I'm arguing against. People in this thread are talking about testing earlier and more often because we have these new tests, not "just" replacing existing tests. The math is very unlikely to work out that we should do that.
- ethbr1 2y ago
  Howso? Existing solutions vs more widely deployed and frequent blood+fecal tests followed up by existing solutions in the case of a potential positive?

cameronh90 2y ago

The emphasis there is on "further treatment". The test itself is broadly benign (except the general risks associated with phlebotomy and any risk of psychological harm). The issue is that doctors often over-react to adverse results due to the risk of being sued if it did turn out to be a true positive. I have two examples of this. One was during a routine blood test I had a liver enzyme flag up, which was then further investigated non-invasively with ultrasound and it was determined that I might either have moderately developed NAFLD (non-alcoholic fatty liver disease, I'm obese) or very early stage NASH (non-alcoholic steatohepatitis) associated fibrosis. The doctor wanted to perform a liver biopsy to confirm which is obviously an invasive procedure with a 1%-ish risk of complications. My response was to ask how the treatment would differ between diagnoses, and he said in either case the treatment would be the same: lifestyle change. He agreed that from a risk perspective the biopsy was just inviting additional risk for no benefit, but that policy is to recommend the test and if I refuse it I'll need to sign an indemnification document saying I was refusing further diagnostics against medical advice. A few years go by, I've made efforts to improve my lifestyle, lost weight, and now my liver tests are all normal proving it was just NAFLD after all. In another case, I had a suspicious finding in an eye test which (long story short) led to me getting two head CT scans which showed no problems. In hindsight, I think a double dose of brain radiation over a common minor finding with no other symptoms was a crazy over-reaction and I would have refused if I had all the facts, but it could have been a life threatening situation in some ridiculously tiny percentage of cases so it was all rush rush and I didn't have time to weigh it up. Often the correct thing to do may be a combination of further non-invasive testing, repeating the test (possibly after a period of time), and "watchful waiting". Doctors often don't feel comfortable with the level of personal risk that could expose them to, and for good reason. That is the issue, not the test.

smt88 2y ago
> The issue is that doctors often over-react to adverse results due to the risk of being sued if it did turn out to be a true positive. Do you think a patient is going to receive a false positive and accept a response from a doctor of, "Oh, might be a false positive. Let's ignore it and not do any more risky testing."? That scenario makes no sense from either perspective. If you get a positive, you do more testing (or skip to treatment). Your examples are well-taken and I understand them, but they don't apply to cancer. When you detect cancer with any test, you immediately do something risky: either a further test that involves risk, or treatment that involves a lot of risk.