Abstract: The present invention is directed to methods for treatment of malignancies in companion animals employing dianhydrogalactitol, diacetyldianhydrogalactitol, and dibromodulcitol, as well as analogs and derivatives thereof, in addition to a method to improve the efficacy and/or reduce the side effects of the administration of a therapeutic agent selected from the group consisting of dianhydrogalactitol, a derivative of dianhydrogalactitol, diacetyldianhydrogalactitol, a derivative of diacetyldianhydrogalactitol, dibromodulcitol, and a derivative of dibromodulcitol to a veterinary subject, the method comprising the steps of: (1 (identifying at least one factor or parameter associated with the efficacy and/or occurrence of side effects of the administration of the therapeutic agent to the veterinary subject; and (2) modifying the factor or parameter to improve the efficacy and/or reduce the side effects of the administration of the therapeutic agent to the veterinary subject.