We assume he got pneumonia in hospital which meant the surgery could not occur. The pneumonia then became more virulent & nothing could be done.
We have no information on whether he was buried or cremated. There were a couple of suggestions which could not be substantiated.
For those who are still assuming he had surgery please read this:
At the time, Frey had a flare-up of intestinal problems he’d struggled with for years, Azoff said, and was hospitalized with plans for surgery. But he developed pneumonia and never was strong enough to undergo that procedure.
http://www.latimes.com/entertainment...118-story.html