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.
