This question is difficult on several levels. When I was diagnosed with prostate cancer I was already retired. I did not have to deal with the prejudice of an employer. Despite laws that prohibit discrimination, you and I know that your health is a major part of how you are evaluated for a position. On some levels I can even sympathize with a potential employer. He/she wants someone who can "hit the ground running", there is always some doubt that a person recovering from cancer can do the job that they want. In addition the insurance industry is the very large elephant in the office. They do not want any company to hire a potentially expensive employe. The medical insurance companies will do all they can to eliminate high risk employees. That is another ugly issue that I won't discuss now.
We all know that is wrong, but it is a fact. So, I would feel very comfortable in suggesting that future employers and insurers be given as little information as possible. As little information as legally possible..
Another area about disclosure is more personal. Do you tell your friends and relatives? My answer from the very beginning has been yes. I proudly wear my blue ribbon pin on my golf hat and lapel. I have some close friends who were diagnosed and treated about the same time that I was. Some are very open about their experience, and others refuse to discuss it with anyone, including fellow prostate cancer victims. Aside from the rather insensitive who ask "if you can still get it up", most people I talk to want to be educated about prostate cancer.
So... I would say that we should all try to help by talking openly about prostate cancer. However, when we are aware that ignorance might hurt our career chances we should say as little as possible.