They’re a secondary sexual characteristic, so it seems like something that would get attention.
There is a super depressing story of a YouTuber named Leathersmokemi who died engaging in a similar fetish. Nick Crowley did a good video on him. I don’t know of a fetish centered on prostate cancer specifically but there are cancer fetishists and the fetish centered on terminal illness is called nosaphillia so it’s certainly possible that there are fetishists already out there focused on prostate cancer specifically.