It's a dark and terribly lonely day for all of us when we first receive a diagnosis of cancer. But, as Purgatory says, the fear can often be relieved by learning all we can about the disease and how to confront it. We have some men (and women) on this site who can share their stories about battling advanced prostate cancer (together). Don't give up hope. Take a deep breath, maybe say a prayer or two, and wait and read what they have to say to you.
My wife and I shed many tears the day we learned of the cancer. Like you, I initially thought, "Why me," but later as Cardinal Joseph Bernardin here in Chicago said, "Why not me?" Bad things happen to good people. This site is illustrative of that fact. But, there is no reason to feel hopeless or powerless.
I'm not an expert on this disease...just someone who has been forced to deal with it. But we have some pretty expert people here, and I'm sure they'll post as soon as they see your comments. As Purgatory said, though, more info on your husband's age, his general health, and his biopsy report would be of great help.
Stay strong and stay positive!