I saw an article with dates last year. I didn't keep the link.
According to it, Rudy dropped out of the race in the early spring, but didn't actually undergo treatment until the late summer, early fall.
That is a disparity that could have significance, especially if the Clinton camp has a bombshell they can explode after the Conventions and before the election.
Politics is dirty, after all. Leave no stone unturned or it could swift boat a candidate.
IMO that wouldn't have much of an effect on Rudy's race even if it were somehow injected into the campaign as a negative.
As for Rudy being able to handle the toughness of politics, any person that can take on the mob (as a prosecutor) and win can certainly handle Hillary.