Spanish tenor Jose Carreras has announced that the proceeds of his charity concert at the Vatican on Dec. 9 will go to fight the disease Carreras himself was stricken with last year: leukemia. The Italian Assn. Against Leukemia, which will primarily benefit from the Carreras benefit, said Monday the revenues would go toward building hospitality centers in Italy for families of leukemia patients. The concert at the Vatican is unusual in that it will feature the South American Creole Mass, a combination of folk and classical elements. Carreras was treated last year in Spain and the United States for the blood disorder, and his doctors told him he is in complete remission.