The analogy is valid, but the difference is not minor.
With infectious disease, if there are ten possible mutations to make the pathogen resistant to treatment, each with a 1% chance of happening within the course of the disease in one patient, then pretty soon all mutations would be present in most of the whole pathogen population on Earth, because of natural selection.
With non-infectious diseases such as cancer, in the same scenario, there would be about a 10% chance of the cancer cells developing one or more of the mutations in each patient, period. A tragedy for those 10% of patients, but a cure for the other 90%.
you're missing the point. cancer is internally infectious. Primary tumors don't even really kill people that much- patients almost always die from metastases. These metastases typically are more resistant.
Please read the entire book "Molecular Biology of Cancer". I'm just explaining small parts of it.
I guess the question then becomes: can the cancer cell population in a single patient evolve fast enough to evade the newly improved immune system, before it gets killed off completely?
It seems unlikely. The genetic diversity was already created. Even when people report "we cannot detect any cancer cells in this person's body, so they're cured", they aren't saying there are no repositories in the body that harbor some resistant cells, whcih will then go walk up the exponential growth curves every aggressive tumor always does.
With infectious disease, if there are ten possible mutations to make the pathogen resistant to treatment, each with a 1% chance of happening within the course of the disease in one patient, then pretty soon all mutations would be present in most of the whole pathogen population on Earth, because of natural selection.
With non-infectious diseases such as cancer, in the same scenario, there would be about a 10% chance of the cancer cells developing one or more of the mutations in each patient, period. A tragedy for those 10% of patients, but a cure for the other 90%.