At the limit though this argument works for broken legs too. Oh sure the leg seems better now, but it could break again. I think with a broken leg you'd accept that's just a different break, even if it's the same leg.

I had Hodgkin's Lymphoma many years ago, in my final follow up they said the radiation damage means there's a higher than normal chance I'd get some entirely different cancer later in life, but as to Hodgkin's there's no difference from the rest of the population. If I get Hodgkin's again it isn't because the treatment stopped working, it just means the same or similar freak DNA change happened. Like if I broke the same leg again.