At 71, James Brown may still think of himself as the hardest working man in show business; as a result he's not even going to let prostate cancer slow him down. Brown acknowledged he has the ailment in a statement to the Associated Press, saying, ''I have overcome a lot of things in my life. I will overcome this as well.'' The announcement came Friday, the night after he finished a two-week tour of Canada. Brown, who's also a diabetic, will undergo cancer surgery on Dec. 15. After a three-week convalescence, he's still planning to make promotional appearances next month to plug his upcoming autobiography, I Feel Good: A Memoir of a Life of Soul. Then he's due to go back on the road in early 2005 with a tour of Australia and Asia. That's the kind of schedule that could leave even younger performers in a cold sweat.