How Often Does An Enlarged Prostate Turn Cancerous?

My brother has just been diagnosed with an enlarged prostate and they will be doing a biopsy to rule out cancer as there is a history on our father s side of the Family and he is 74 years old. What we are wondering is , are there any numbers on how often an enlarged prostate turns into cancer? Also i am 62 and have been cancer free for 6 years after having my prostate removed. I had 2 biopsy but did not have to clean out my bowel, yet they have told my brother he will need to preform an enema before the biopsy. Is this a common practice for some doctors?