I know, it is an imperfect analogy. But thank you for noticing and explaining my shortcut to other readers.
Cancers are very patient-specific, and the main threat with immunotherapy is that the targeted cancer adapts quickly enough to escape the immune system again.
>Cancers are very patient-specific, and the main threat with immunotherapy is that the targeted cancer adapts quickly enough to escape the immune system again.
(I'm just an interested party and don't have any formal training on the subject.) I'm sure there are technical terms for it, but from what I've read the lack of regulatory features in the replication process of cancer cells tends to accumulate more mutations and genetic damage through each generation. PARP-inhibitors, for example, help fight cancer by suppressing DNA repair enzymes and letting the cancer cells get into non-viable states more often than healthy tissue.
In general though, this genetic entropy/volatility creates a scenario where adaptations can happen quite quickly.
Those treatment resistances are quite different. Resistant bacteria spread to other people, while cancer is almost always limited to a single patient. So it the treatment works for a certain fraction of cancers, it'll stay at that level, unlike bacteria which become increasingly resistant over time.
(I guess that in the very long term that might not be true, since natural cancer resistance will offer less of an evolutionary advantage. But that assumes that humanity will remain in a similar state as currently, which seems unlikely.)