Vincristine sulfate as single-agent chemotherapy in a dog and a cat with malignant neoplasms.

A 12-year-old 4-kg spayed domestic shorthair cat with a poorly differentiated fibrosarcoma of the rostral aspect of the mandible and an 11-year-old 13-kg castrated dog of mixed breeding with pulmonary metastatic hemangiosarcoma were treated with 0.5 mg of vincristine sulfate/m2 of body surface, IV, weekly. Three months after beginning treatment, both animals had complete clinical remission. The role of this vinca alkaloid as a single agent for malignant neoplasms has seldom been discussed in the veterinary scientific literature. The results of these two cases indicate that single-agent vincristine sulfate chemotherapy is effective in the treatment of feline fibrosarcoma and canine hemangiosarcoma.