Men with prostate cancer rarely die because of the cancer unless it's diagnosed very late and there is extensive metastasis. AFAIK, Rudy's cancer was caught early.
The pubbies did much to persuade Rudy to go for the Senate, and especially, oppose the spouse of the Bent One. With his marriage difficulties and the cancer, he had an easy excuse to back out of a tough race for a job that he is not tempermentally suited. He already had a loss to Dinkins in a close race in 1989. Forgive me if I sound like a broken record, but Rudy has his sights on Albany, IMHO.