melbabes,
Sorry to hear about your father.
I don't think anyone can say much without more information. "back" isn't a very precise location, and nothing you've said confirms prostate cancer at all. Lots of men have enlarged prostates, but don't have cancer.
What symptoms did he have, or what caused him to go for investigations in the first place?
If they have any slight suspicion of prostate cancer, he woul have had a PSA blood test. Do you know what the result was?