Is Maintenance Chemotherapy Appropriate for the Management of Canine Malignant Lymphoma

A retrospective study was conducted between two groups of dogs with histopathologically diagnosed multicentric malignant lymphoma to determine if treatment with either short-term or continuous chemotherapy resulted in a significant difference in first-remission length or survival time. One group was treated with single agent, short-term (three cycles) of doxorubicin.* Dogs obtaining complete remission while receiving doxorubicin were given no further chemotherapy. The other group received combination agent, long-term chemotherapy consisting of cyclophosphamide,† vincristine sulfate,‡ and prednisone (COP). Dogs obtaining complete remission on COP by the end of 6 weeks were given maintenance chemotherapy of cyclophosphamide, prednisone and methotrexate.§ One hundred and five dogs were treated. Thirty-eight dogs received doxorubicin and 67 received COP. All dogs were evaluated at 6 weeks for response to chemotherapy and followed until death. No significant differences were observed in first-remission length or survival time when comparing dogs treated with either short-term doxorubicin or long-term COP (P > 0.05). Sex, weight, age, clinical stage, performance status, histopathologic cell type, and grade were not significant factors for determining the responsiveness to either chemotherapy protocol. However, within either treatment group, significant differences in first-remission length were observed in dogs evaluated histopathologically by the Keil and NCI working formulation and in survival time when evaluated by performance status (P < 0.05). (Journal of Veterinary Internal Medicine 1992; 6:3–10)