7 ms·

Is there any reason why we don't do full-body scans on a regular basis? Is it too much radiation? It seems to me that (a) this is the only way to deal with sile

Is there any reason why we don't do full-body scans on a regular basis? Is it too much radiation? It seems to me that (a) this is the only way to deal with silent cancers like many pancreatic kinds that are discovered at Stage IV (at which point, the prognosis is terrible) and (b) it would be cheaper to do the scans than to deal with the (expensive, and often ineffective) late stage cancers. I'd imagine that there was a time when this was impractical because of the amount of radiation involved, but is that still the case? Don't we have extremely low-radiation X-ray devices that can make regular full-body scans a reality?

toufka 12y ago
Scanning is still fairly invasive (w.r.t. radiation/dosages). And in general, the better the resolution, the more damaging. The bigger reason we don't continually scan people is that everyone has all sorts of little cancerous growths that are entirely benign. They would show up on these scans and freak people out. And often the overreaction of invasively removing those tiny little benign cancers can cause more problems. Don't misuse or abuse this information, but in general the 'abnormal growths' in a person are just that. They do very little and are just little bugs in the system. But the overall system is capable of dealing with them. It's the rare kind that is able to get around the entire body's defenses. But unfortunately it's difficult to tell which/when that happens. But again, if you took whole body scans all the time, and tried to root out all those little growths, you'd cause a lot more harm than good.
- mikecsh 12y ago
  >Scanning is still fairly invasive (w.r.t. radiation/dosages). And in general, the better the resolution, the more damaging. This guy had MRI scans which don't rely on ionising radiation and have no known adverse effects. >everyone has all sorts of little cancerous growths that are entirely benign When discussing tumours, cancerous and benign mean different things. You cannot have a benign cancerous growth. I think the main reason people aren't scanned routinely is due to the enormous cost of the scanning and the data analysis that currently relies on physicians for interpretation. My personal view is that with ever decreasing costs of MRI and improvements in computer vision and diagnostic algorithms, this could become a viable process in the future. As for not over-treating, that is a physician led decision - just because there is an anomaly on the scan does not mean that it will be removed or even necessarily treated at all.
  - throwaway47385 12y ago
    > This guy had MRI scans which don't rely on ionising radiation and have no known adverse effects. http://www.ncbi.nlm.nih.gov/pubmed/21412810 http://www.ncbi.nlm.nih.gov/pubmed/21412810 Also, the price of a single scan is measured in thousands of dollars.
    - sghodas 12y ago
      I skimmed that study, but it looks like all the samples they tested came from the same guy, and they didn't actually test putting people in MRIs.
      - throwaway47385 12y ago
        Yes, the authors did base their paper on in vitro tests from a single individual. Another group attempted to reproduce the results of Lee, et al by performing a similar in vitro experiment, but failed to detect any DNA damage.[1] Nevertheless, in an article commentary published by the European Society of Cardiology [2], DNA damage was detected in an in vivo study of Cardiac MR (CMR) imaging, and a precautionary approach to MR imaging is recommended. They admit, though, that the study could not differentiate between the effects of the contrast agent used in CMR, and the effects MR imaging alone. [1] http://www.ncbi.nlm.nih.gov/pubmed/23679232 http://www.ncbi.nlm.nih.gov/pubmed/23679232 [2] http://eurheartj.oxfordjournals.org/content/34/30/2337 http://eurheartj.oxfordjournals.org/content/34/30/2337
  - a_c_s 12y ago
    While you are technically correct, it appears you've missed the point: being able to detect tumors better doesn't improve lifespan if we end up aggressively treating benign ones. This isn't a theoretical problem, rather one we are seeing right now. Look at thyroid cancer: detection and treatment rates are much higher than they used to be but the death rate has remained steady. Source: http://www.nytimes.com/2014/11/06/health/study-warns-against-overdiagnosis-of-thyroid-cancer.html?_r=0 http://www.nytimes.com/2014/11/06/health/study-warns-against...
- rudolf0 12y ago
  If this technology came with a feature to easily biopsy all the growths and tumors, and send them to a lab, do you think it would be beneficial then?
  - toufka 12y ago
    There's a significant school of thought that the structure of biological material helps ensure it works properly, and that an otherwise benign feature might actually become more harmful when their local environment is disturbed (possibly, by a biopsy). Biopsies are a very useful tool, but you don't want to do lots and lots of them if you can help it.
    - rudolf0 12y ago
      I understand, but I think medical technology is inevitably moving in the direction of some degree of consistent self-testing and monitoring, and I expect small biopsies of suspicious masses will eventually be implemented in a way that causes almost no structural changes. I think this is how average lifespans are going to start rising dramatically in the next few centuries, but it's going to be a long and slow process.
foobarqux 12y ago
CT scans expose you to about 100-1000x the radiation of a single x-ray but that isn't the main reason frequent tests aren't done. The main reason based on my understanding is two-fold: First, cost would be prohibitive, and second the absolute number of false positive would do more harm than good overall.
- shas3 12y ago
  I wonder if the relative rate and effect of false alarms is constant or if it increases as a function of how frequently scans are done. This is related to what studies are finding about cancer screenings. The more screenings you have, the time at which potential tumors are spotted is pushed back, and more non-dangerous tumors are caught. These benign tumors are mistakenly treated as malignant tumors because they were detected too early. I would imagine something similar would happen if people went for all out CT-scans.
mbreese 12y ago
In addition to the radiation, which can also induce cancer, you don't want to go scanning for things without a good reason. The false positive rates would increase a lot and you'd end up worrying a bunch of people for no good reason. Not to mention, you'd then have to have secondary biopsies or scans for these people, and those are not without risk. Let's say that you had a low-radiation source imaging device that only had a 0.01% chance of causing cancer (I don't know the actual rates, so this is just a hypothetical). If you only get the scans when needed, you might only have 10,000 people getting the scan in a year. That means you'd have roughly 1 radiation induced cancer, and that would be in a patient that was already undergoing some form of treatment. Now let's say that you open up the criteria for who can get a scan. So instead of the 10,000, you now have 1,000,000 people. Now you have 100 people that will get a radiation induced cancer. While each of them has a low risk, the risk for the population is still too high to warrant unrestricted testing. MRI's are a different beast, but you still have the risks of worrying a bunch of people that may not have anything wrong with them. And then there are the costs involved - both in terms of $$$ and time. For each healthy person getting a prophylactic MRI, a sick person would have to wait.
hashmymustache 12y ago
Even urine screening would be excessive on a regular basis. The pretest probability is too low in the general population for mosts tests that even with incredibly high sensitivity and specificity the positive predictive value sucks due to all the false positives. This adds up into undue stress and unnecessary economic burden. Edit: Just to add, low dose CT was recently approved for lung cancer screening from a study which showed increased detection and survival for patients 55-80 yrs old with at least a 30-pack year history (20 cigarettes per day for 30 years). All that said, screenings will ultimately be grounded in genetics more than lifestyle as we become more preventative focused. This also adds granularity to pre-test probabilities of screening tests to ensure they are useful for the population tested.
kgwgk 12y ago
There are multiple reasons, not only the direct harm from radiation. The latest book from Dr. Welch "Less medicine, more health : 7 assumptions that drive too much medical care" explains some of them. The table of contents provides a good summary of his message: ASSUMPTION #1: ALL RISKS CAN BE LOWERED Disturbing truth: Risks can’t always be lowered—and trying creates risks of its own ASSUMPTION #2: IT’S ALWAYS BETTER TO FIX THE PROBLEM Disturbing truth: Trying to eliminate a problem can be more dangerous than managing one ASSUMPTION #3: SOONER IS ALWAYS BETTER Disturbing truth: Early diagnosis can needlessly turn people into patients ASSUMPTION #4: IT NEVER HURTS TO GET MORE INFORMATION Disturbing truth: Data overload can scare patients and distract your doctor from what’s important ASSUMPTION #5: ACTION IS ALWAYS BETTER THAN INACTION Disturbing truth: Action is not reliably the “right” choice ASSUMPTION #6: NEWER IS ALWAYS BETTER Disturbing truth: New interventions are typically not well tested and oft en wind up being judged ineffective (even harmful) ASSUMPTION #7: IT’S ALL ABOUT AVOIDING DEATH Disturbing truth: A fixation on preventing death diminishes life
- seagreen 12y ago
  This seems like a repetition of the same point seven times. Let me try to rephrase your seven assumptions into a single, strong argument: "Doctors and patients treat intervention as the default response to medical issues, but there are situations where intervention is (on average) neutral or harmful." This is true. It is not a strong argument against medical scans however[1]. For instance, the result of the scans could be analyzed by a third party who isn't the patient or the doctor. Issues could only be passed along to the doctor if it will lead to a statistically better outcome for the patient. [1] It might be a strong argument given a sufficiently weak culture, for instance one that is unable to provide legal immunity to the statistics-running third party. If your argument is, "We suck so bad we can't do 'statistics', so putting our heads in the sand is actually the best outcome we can get", you can just say that directly. EDIT: Changed "can't" to "can". Thanks kgwgk.
  - kgwgk 12y ago
    > If your argument is, "We suck so bad we can't do 'statistics', so putting our heads in the sand is actually the best outcome we can't (?) get", you can just say that directly. As far as I know, the statistics we have show that it is better to avoid doing full-body CT scans to asymptomatic people in the first place. Maybe you have different statistics?

toufka 12y ago

Scanning is still fairly invasive (w.r.t. radiation/dosages). And in general, the better the resolution, the more damaging. The bigger reason we don't continually scan people is that everyone has all sorts of little cancerous growths that are entirely benign. They would show up on these scans and freak people out. And often the overreaction of invasively removing those tiny little benign cancers can cause more problems. Don't misuse or abuse this information, but in general the 'abnormal growths' in a person are just that. They do very little and are just little bugs in the system. But the overall system is capable of dealing with them. It's the rare kind that is able to get around the entire body's defenses. But unfortunately it's difficult to tell which/when that happens. But again, if you took whole body scans all the time, and tried to root out all those little growths, you'd cause a lot more harm than good.

mikecsh 12y ago
>Scanning is still fairly invasive (w.r.t. radiation/dosages). And in general, the better the resolution, the more damaging. This guy had MRI scans which don't rely on ionising radiation and have no known adverse effects. >everyone has all sorts of little cancerous growths that are entirely benign When discussing tumours, cancerous and benign mean different things. You cannot have a benign cancerous growth. I think the main reason people aren't scanned routinely is due to the enormous cost of the scanning and the data analysis that currently relies on physicians for interpretation. My personal view is that with ever decreasing costs of MRI and improvements in computer vision and diagnostic algorithms, this could become a viable process in the future. As for not over-treating, that is a physician led decision - just because there is an anomaly on the scan does not mean that it will be removed or even necessarily treated at all.
- throwaway47385 12y ago
  > This guy had MRI scans which don't rely on ionising radiation and have no known adverse effects. http://www.ncbi.nlm.nih.gov/pubmed/21412810 http://www.ncbi.nlm.nih.gov/pubmed/21412810 Also, the price of a single scan is measured in thousands of dollars.
  - sghodas 12y ago
    I skimmed that study, but it looks like all the samples they tested came from the same guy, and they didn't actually test putting people in MRIs.
    - throwaway47385 12y ago
      Yes, the authors did base their paper on in vitro tests from a single individual. Another group attempted to reproduce the results of Lee, et al by performing a similar in vitro experiment, but failed to detect any DNA damage.[1] Nevertheless, in an article commentary published by the European Society of Cardiology [2], DNA damage was detected in an in vivo study of Cardiac MR (CMR) imaging, and a precautionary approach to MR imaging is recommended. They admit, though, that the study could not differentiate between the effects of the contrast agent used in CMR, and the effects MR imaging alone. [1] http://www.ncbi.nlm.nih.gov/pubmed/23679232 http://www.ncbi.nlm.nih.gov/pubmed/23679232 [2] http://eurheartj.oxfordjournals.org/content/34/30/2337 http://eurheartj.oxfordjournals.org/content/34/30/2337
- a_c_s 12y ago
  While you are technically correct, it appears you've missed the point: being able to detect tumors better doesn't improve lifespan if we end up aggressively treating benign ones. This isn't a theoretical problem, rather one we are seeing right now. Look at thyroid cancer: detection and treatment rates are much higher than they used to be but the death rate has remained steady. Source: http://www.nytimes.com/2014/11/06/health/study-warns-against-overdiagnosis-of-thyroid-cancer.html?_r=0 http://www.nytimes.com/2014/11/06/health/study-warns-against...
rudolf0 12y ago
If this technology came with a feature to easily biopsy all the growths and tumors, and send them to a lab, do you think it would be beneficial then?
- toufka 12y ago
  There's a significant school of thought that the structure of biological material helps ensure it works properly, and that an otherwise benign feature might actually become more harmful when their local environment is disturbed (possibly, by a biopsy). Biopsies are a very useful tool, but you don't want to do lots and lots of them if you can help it.
  - rudolf0 12y ago
    I understand, but I think medical technology is inevitably moving in the direction of some degree of consistent self-testing and monitoring, and I expect small biopsies of suspicious masses will eventually be implemented in a way that causes almost no structural changes. I think this is how average lifespans are going to start rising dramatically in the next few centuries, but it's going to be a long and slow process.

foobarqux 12y ago

CT scans expose you to about 100-1000x the radiation of a single x-ray but that isn't the main reason frequent tests aren't done. The main reason based on my understanding is two-fold: First, cost would be prohibitive, and second the absolute number of false positive would do more harm than good overall.

shas3 12y ago
I wonder if the relative rate and effect of false alarms is constant or if it increases as a function of how frequently scans are done. This is related to what studies are finding about cancer screenings. The more screenings you have, the time at which potential tumors are spotted is pushed back, and more non-dangerous tumors are caught. These benign tumors are mistakenly treated as malignant tumors because they were detected too early. I would imagine something similar would happen if people went for all out CT-scans.

mbreese 12y ago

In addition to the radiation, which can also induce cancer, you don't want to go scanning for things without a good reason. The false positive rates would increase a lot and you'd end up worrying a bunch of people for no good reason. Not to mention, you'd then have to have secondary biopsies or scans for these people, and those are not without risk. Let's say that you had a low-radiation source imaging device that only had a 0.01% chance of causing cancer (I don't know the actual rates, so this is just a hypothetical). If you only get the scans when needed, you might only have 10,000 people getting the scan in a year. That means you'd have roughly 1 radiation induced cancer, and that would be in a patient that was already undergoing some form of treatment. Now let's say that you open up the criteria for who can get a scan. So instead of the 10,000, you now have 1,000,000 people. Now you have 100 people that will get a radiation induced cancer. While each of them has a low risk, the risk for the population is still too high to warrant unrestricted testing. MRI's are a different beast, but you still have the risks of worrying a bunch of people that may not have anything wrong with them. And then there are the costs involved - both in terms of $$$ and time. For each healthy person getting a prophylactic MRI, a sick person would have to wait.

hashmymustache 12y ago

Even urine screening would be excessive on a regular basis. The pretest probability is too low in the general population for mosts tests that even with incredibly high sensitivity and specificity the positive predictive value sucks due to all the false positives. This adds up into undue stress and unnecessary economic burden. Edit: Just to add, low dose CT was recently approved for lung cancer screening from a study which showed increased detection and survival for patients 55-80 yrs old with at least a 30-pack year history (20 cigarettes per day for 30 years). All that said, screenings will ultimately be grounded in genetics more than lifestyle as we become more preventative focused. This also adds granularity to pre-test probabilities of screening tests to ensure they are useful for the population tested.

kgwgk 12y ago

There are multiple reasons, not only the direct harm from radiation. The latest book from Dr. Welch "Less medicine, more health : 7 assumptions that drive too much medical care" explains some of them. The table of contents provides a good summary of his message: ASSUMPTION #1: ALL RISKS CAN BE LOWERED Disturbing truth: Risks can’t always be lowered—and trying creates risks of its own ASSUMPTION #2: IT’S ALWAYS BETTER TO FIX THE PROBLEM Disturbing truth: Trying to eliminate a problem can be more dangerous than managing one ASSUMPTION #3: SOONER IS ALWAYS BETTER Disturbing truth: Early diagnosis can needlessly turn people into patients ASSUMPTION #4: IT NEVER HURTS TO GET MORE INFORMATION Disturbing truth: Data overload can scare patients and distract your doctor from what’s important ASSUMPTION #5: ACTION IS ALWAYS BETTER THAN INACTION Disturbing truth: Action is not reliably the “right” choice ASSUMPTION #6: NEWER IS ALWAYS BETTER Disturbing truth: New interventions are typically not well tested and oft en wind up being judged ineffective (even harmful) ASSUMPTION #7: IT’S ALL ABOUT AVOIDING DEATH Disturbing truth: A fixation on preventing death diminishes life

seagreen 12y ago
This seems like a repetition of the same point seven times. Let me try to rephrase your seven assumptions into a single, strong argument: "Doctors and patients treat intervention as the default response to medical issues, but there are situations where intervention is (on average) neutral or harmful." This is true. It is not a strong argument against medical scans however[1]. For instance, the result of the scans could be analyzed by a third party who isn't the patient or the doctor. Issues could only be passed along to the doctor if it will lead to a statistically better outcome for the patient. [1] It might be a strong argument given a sufficiently weak culture, for instance one that is unable to provide legal immunity to the statistics-running third party. If your argument is, "We suck so bad we can't do 'statistics', so putting our heads in the sand is actually the best outcome we can get", you can just say that directly. EDIT: Changed "can't" to "can". Thanks kgwgk.
- kgwgk 12y ago
  > If your argument is, "We suck so bad we can't do 'statistics', so putting our heads in the sand is actually the best outcome we can't (?) get", you can just say that directly. As far as I know, the statistics we have show that it is better to avoid doing full-body CT scans to asymptomatic people in the first place. Maybe you have different statistics?