Of intracranial tumors, primary central nervous system lymphoma (PCNSL) is rare in dogs. Herein, we describe our experience with two dogs (a 3-year-old intact female toy poodle and a 5-year-old spayed female toy poodle) that developed neurological symptoms. Magnetic resonance imaging (MRI) revealed intracranial disseminated lesions. Cerebrospinal fluid (CSF) examination revealed pleocytosis and B-cell monoclonal proliferation in both cases. PCNSL or secondary central nervous system lymphoma (SCNSL) was diagnosed on the basis of MRI findings and CSF examinations. Nimustine (ACNU) is a nitrosourea alkylating agent, a class of drugs that includes lomustine. Nimustine is mainly used to treat human intracranial neoplasia because of its high permeability across the blood-brain barrier. The dogs in this study were treated with combined chemotherapy comprising nimustine and prednisolone, which achieved complete or nearly complete remission of neurological symptoms and long-term survival (>2583 days and 1218 days), but with problematic adverse effects. We determined that the dose of nimustine for canine PCNSL or SCNSL with intravenous infusion was 25-30 mg/m2 every 3-4 weeks for a total of four times; however, the data were insufficient to determine the optimal regimen.
Keywords: canine; chemotherapy; intracranial; lymphoma; nimusutine.