But cancer isn't an organism. Cancer cells in any specific individual may evolve that way, but "human cancers" as a group will not. (The only way they could is by evolving human DNA, but "survival of the fittest" pushes the opposite direction for that.)
Indeed, there's no "be a better/stronger cancer and spread more effectively to more hosts" the way there is with bacteria or a virus. It's not like the flu where we need a new shot every winter because every winter is a new flu.
Once we solve the cancers we know about, they're solved forever, with the one caveat that more people will live longer, so that will increase the window for eventually still ending up dying to one of the cancers that happens to have a non-evolved built in resistance to this or that treatment. Which is a great deal of course, especially if it's a treatment that sounds way less destructive of QoL than chemo, radiation, etc.
>there's no "be a better/stronger cancer and spread more effectively to more hosts"
No, but there is "be a better/stronger cancer cell and don't succumb to whatever therapy is killing its neighboring cells." It's exactly akin to how dosing isolated populations of bacteria with antibiotics selects for individual cells that are resistant, which then multiply and dominate [0], just like a tumor.
[0] https://www.youtube.com/watch?v=plVk4NVIUh8
Right, but that's within a single host isn't it? Like patient A gets that mutation and succumbs, that sucks, but the stronger cancer cells don't them jump to patient B the way antibiotic-resistant bacteria do.
(barring the transmissible cancers article that your sibling comment linked to, but that's not the common case)
> Indeed, there's no "be a better/stronger cancer and spread more effectively to more hosts" the way there is with bacteria or a virus.
The rare exception: https://en.wikipedia.org/wiki/Clonally_transmissible_cancer
Well that's terrifying, TIL.
It's not very relevant here, but curiously some cancers are, in fact, contagious organisms. The most famous example is the devil facial tumour disease. Luckily cases of transmissible cancer in humans are extremely rare (if you count only transmission of cancer itself and not the cancerogenic agents).
Another curious case of "cancer being an organism" is the HeLa line derived from cervical cancer cells taken from a woman called Henrietta Lacks.
Nonetheless, we see the exact same resistance mechanisms to the same therapies recur across individuals, e.g. [0]. Convergent evolution is a harsh mistress.
[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC2538882/