Yes, but when you compare treatments A vs B for trial 1, and then B vs C for trial 2, and then C, vs D for trail 3, you might not get the same results as comparing A vs D, especially when there may have been other changes in between the three trials (different ages, lifestyles etc).
This is a real problem when the Minister wants to know if it’s worth spending money on treatments, because all you have is a disjointed set of trials, none of which are necessarily representative of the population at large, or the population wide incidence of the disease (assuming there is even data on that (notifiable illnesses are the exception).
> Yes, but when you compare treatments A vs B for trial 1, and then B vs C for trial 2, and then C, vs D for trail 3, you might not get the same results as comparing A vs D, especially when there may have been other changes in between the three trials (different ages, lifestyles etc).
That's not what happens.
Is this just a hypothetical?
Everything will be compared to one standard of care, or perhaps two which will have been compared to each other. If a new treatment is much better, then it will become standard of care.
Trials cost a lot of money, so they are conducted rationally.
That is what happens if C is developed after B becomes the standard treatment, D after C etc.
Suppose D is only slightly less effective than C, but more effective than A, and B, but 100x cheaper, and/or has less bad side effects. If you only compare with C, all you know is it's not as good as C.
> That is what happens if C is developed after B becomes the standard treatment, D after C etc.
Can you point to particular drugs or are you also making up examples?
I admittedly do not know of every trial that happens everywhere but this is exactly the sort of thing that a layman expects would occur but which does not happen.
Stem cell treatments come to mind. Outrageously expensive (or outright unavailable locally), in many areas and for select purposes.
> Stem cell treatments come to mind. Outrageously expensive (or outright unavailable locally), in many areas and for select purposes.
I don't see how stem cells relate to the idea of trials for successive standard-of-care treatments. Can you explain your thinking?