I was wondering the same thing. Vaccination means exercising against a mockup foe before meeting the real enemy. But the cancer patient is already deep into the

I was wondering the same thing. Vaccination means exercising against a mockup foe before meeting the real enemy. But the cancer patient is already deep into the battle, how could adding mockup enemies help winning? Perhaps the molecules they want the immune system to attack aren't sufficiently mobile, sticking to the tumor instead of diffusing into the entire body? From what I've picked up in the pandemic the immune system has a dedicated proving ground spots where experimentation is happening, and relies on special cells to transport foe candidates into those proving grounds (just like a programmer would gather problematic input samples in their unit tests). Maybe the tumor bits they want attacked cannot be transported to "lab organ", but fragments created separately, from mRNA injections, could, and once the immune system is producing antibodies against those fragments they will also react with the immobile real tumor bits. Purely speculative on my part, but maybe it really is something along those lines?