Nice.

Er, no. Cancer is a buildup of overgrown rogue cells, not of rotten sperm. Sperm could be indirectly responsible if it were carcinogenic (causing other cells in the prostate to mutate and become cancerous), but it isn't, so that's not it either. Even if one or both of these WERE true, sperm is stored in the cauda region of the epididymis, not the prostate. And lastly, at least when functioning properly, males will eject sperm naturally in their sleep ("wet dreams") if they are not ejaculating regularly in their day to day lives, which would make buildup of "rotten sperm" impossible anyway at least to a point. You're actively misinforming people about both cancer AND the male reproductive system. Since I infer from your screen name you lack the latter, and from simple hope that you lack the former, I encourage you to exercise a little more care in checking your information against reliable sources, instead of just blandly trusting friends/the internet. It's a lot harder to verify this kind of information when you lack the experience and/or anatomy involved, so it means you need to check your facts more cautiously.