4 ms·

Can a doctor reliably tell when a prostate cancer is likely to become dangerous?

pintxo 3y ago
There are good indicators yes. E.g. PSA (a blood value, easy to measure), if increasing very slowly over a long timeframe, is a good indicator that you may have cancer but that it is growing really slow, aka unlikely to be aggressive and to be an immediate problem. While a quick increase tells you the opposite. Then there is DNA sequencing of cancer samples from a Biopsy. Which is evolving rapidly and should be soon cheap enough to be available at scale.
- evandijk70 3y ago
  AFAIK there is currently know way to reliably tell from DNA sequencing data whether a prostate cancer will become dangerous. That may change, but I suspect there may be some inherent stochasticity in the transition of a cancer from benign to dangerous that will make a perfect classification possible. I would guess some form of monitoring may be required for all the currently non-dangerous cancers.
  - pintxo 3y ago
    Yes, I had a glimpse at current research, it’s being worked on, but it’s not yet there. Also sequencing is still too expensive for more general application.
    - dumb1224 3y ago
      Genotyping assays for single nucleotide polymorphisms (SNPs) are relatively cheaper (I may not be up to date). In the space of 'polygenic risk score' of these genomice variants it is still a bit of debate how useful it is for screening.
tptacek 3y ago
The article addresses this. There's some risk of misclassification, but the answer is the same either way: you monitor the condition carefully to see how it behaves. The problem then is, if you rename the "grade 1" condition "prostate dysplasia", some fraction of patients don't do the follow-ups, and then those misclassifications are a big deal. But if you don't rename it, some fraction of patients get unnecessary treatment that lowers their quality of life. So it's an interesting dilemma.
- andersrs 3y ago
  3Blue1Brown explains it well. https://www.youtube.com/watch?v=lG4VkPoG3ko https://www.youtube.com/watch?v=lG4VkPoG3ko If the population who do _not_ actually have serious cancer is orders of magnitudes larger than those who do then there will be far more people in the false positive group than the true positive group and thus the vast majority of operations will be unnecessary.
  - pintxo 3y ago
    Good one. The key here is how we manage the positive ones. And this is where the current system fails. We have yet to find a good way to manage them without doing unnecessary treatments causing more harm than good. But instead of fixing this problem, we opted to stop screening. Which, for me, sounds stupid. But it sure is easier to do.
  - hef19898 3y ago
    With all due respect to 3Blue1Brown, there are limits to wjat you can explain with statistics. Medicine applied on the individual pevel is one of those cases, because its purpose is to optimize the outcome for the individual. A pandemic is different, there the goal is to optimize the outcome for the population. Applying the latter to the former is at the very least cynical. The opposite is what got us anti-mask and anti-vaxxers. Also, especially with cancer, people tend to be so affraid of the diagnosis, they look for excuses to not be examined. As if cancer onpy pops up when it is found or something. Which is stupid, if ypu have cancer you want to know as early as possible.

There are good indicators yes. E.g. PSA (a blood value, easy to measure), if increasing very slowly over a long timeframe, is a good indicator that you may have cancer but that it is growing really slow, aka unlikely to be aggressive and to be an immediate problem. While a quick increase tells you the opposite. Then there is DNA sequencing of cancer samples from a Biopsy. Which is evolving rapidly and should be soon cheap enough to be available at scale.

evandijk70 3y ago
AFAIK there is currently know way to reliably tell from DNA sequencing data whether a prostate cancer will become dangerous. That may change, but I suspect there may be some inherent stochasticity in the transition of a cancer from benign to dangerous that will make a perfect classification possible. I would guess some form of monitoring may be required for all the currently non-dangerous cancers.
- pintxo 3y ago
  Yes, I had a glimpse at current research, it’s being worked on, but it’s not yet there. Also sequencing is still too expensive for more general application.
  - dumb1224 3y ago
    Genotyping assays for single nucleotide polymorphisms (SNPs) are relatively cheaper (I may not be up to date). In the space of 'polygenic risk score' of these genomice variants it is still a bit of debate how useful it is for screening.

tptacek 3y ago

The article addresses this. There's some risk of misclassification, but the answer is the same either way: you monitor the condition carefully to see how it behaves. The problem then is, if you rename the "grade 1" condition "prostate dysplasia", some fraction of patients don't do the follow-ups, and then those misclassifications are a big deal. But if you don't rename it, some fraction of patients get unnecessary treatment that lowers their quality of life. So it's an interesting dilemma.

andersrs 3y ago
3Blue1Brown explains it well. https://www.youtube.com/watch?v=lG4VkPoG3ko https://www.youtube.com/watch?v=lG4VkPoG3ko If the population who do _not_ actually have serious cancer is orders of magnitudes larger than those who do then there will be far more people in the false positive group than the true positive group and thus the vast majority of operations will be unnecessary.
- pintxo 3y ago
  Good one. The key here is how we manage the positive ones. And this is where the current system fails. We have yet to find a good way to manage them without doing unnecessary treatments causing more harm than good. But instead of fixing this problem, we opted to stop screening. Which, for me, sounds stupid. But it sure is easier to do.
- hef19898 3y ago
  With all due respect to 3Blue1Brown, there are limits to wjat you can explain with statistics. Medicine applied on the individual pevel is one of those cases, because its purpose is to optimize the outcome for the individual. A pandemic is different, there the goal is to optimize the outcome for the population. Applying the latter to the former is at the very least cynical. The opposite is what got us anti-mask and anti-vaxxers. Also, especially with cancer, people tend to be so affraid of the diagnosis, they look for excuses to not be examined. As if cancer onpy pops up when it is found or something. Which is stupid, if ypu have cancer you want to know as early as possible.