Prostate Cancer can cause the prostate gland to swell. This swelling can narrow or restrict the urethra altogether. It is possible to have prostate cancer and not experience any problems with the urethra.
Prostate Cancer is cancer that is found in the Prostate gland of males. As will all Cancer the cause is not known for sure. Http://ehealthmd.com/content/what-prostate-cancer is a great website to explain Prostate Cancer and has information on who may be at risk.