Subject has known contraindication or allergy to both xanthine oxidase inhibitors and rasburicase Known allergy to both xanthine oxidase inhibitors and rasburicase Concomitant therapy with allopurinol and other xanthine oxidase inhibitors Known allergy to xanthine oxidase inhibitors and/or rasburicase for subjects at risk for tumor lysis syndrome Known allergy to both xanthine oxidase inhibitors and rasburicase Known allergy to both xanthine oxidase inhibitors and rasburicase; or, known hypersensitivity to any of the study drugs Known allergy to both xanthine oxidase inhibitors and rasburicase Known allergy to xanthine oxidase inhibitors and/or rasburicase for subjects at risk for TLS Known allergy to both xanthine oxidase inhibitors and rasburicase Subject has known contraindication or allergy to both xanthine oxidase inhibitors and rasburicase. Known allergy to both xanthine oxidase inhibitors and rasburicase