I mean I know some has to be, but it feels kinda like it is the last ditch effort to kill something like with raditation therapy requiring bonemarrow transplant aftward.
It's not a perfect conection, so other cells may be unlucky. The hard part is that cancer cells are too very similar to the original nornal cells, so picking where to stick is difficult.
I'm not sure about this article, but sometimes the problem is solved with custom personalized versions of the drug, but in that case the treatment is very expensive.
And sometimes the trick is to use an atom that is mostly used by some organ, like using radioactve iodine to target thyroid cancer.