Evaluation of 600 mg/m2 cytarabine arabinoside as treatment for meningoencephalomyelitis of unknown origin in 43 dogs.

Abstract

BACKGROUND: Cytarabine arabinoside (CA) is commonly used at 200&#xa0;mg/m2 to treat dogs with meningoencephalomyelitis of unknown origin (MUO); use of higher doses is anecdotally reported. HYPOTHESIS/OBJECTIVES: To describe the clinical outcome in 43 dogs with MUO receiving 600&#xa0;mg/m2 CA. We hypothesized that high dose CA would be well tolerated, that the majority of dogs with MUO would achieve sustained remission, and that dogs with spinal cord-only MUO or presumptive necrotizing meningoencephalitis (NME) would carry a more guarded prognosis. ANIMALS: Forty-three client-owned dogs with MUO. METHODS: Retrospective observational study. Medical records were reviewed at a private practice over a 2.5-year period to identify dogs with MUO with clinical signs <14&#xa0;days and neurological examination and MRI abnormalities suggestive of moderate to severe disease (mild cases excluded). All dogs received 600&#xa0;mg/m2 CA every 3-6&#xa0;weeks for a minimum of 6&#xa0;months or until death. Minimum follow up time was 24&#xa0;months. RESULTS: Twenty-three out of twenty-five (92%) dogs without spinal cord MUO, presumptive NME, or death from other diseases survived >24&#xa0;months (median 1027&#xa0;days, range 770-1277&#xa0;days). Thirteen out of forty-three (30%) dogs were euthanized due to poor disease control (median 17&#xa0;days, range 1-340&#xa0;days), including 5/10 (50%) dogs with spinal cord only MUO and 5/5 (100%) dogs with presumptive NME. No serious adverse events were noted with 600&#xa0;mg/m2 CA. CONCLUSIONS AND CLINICAL IMPORTANCE: Six hundred mg/m2 CA was well tolerated and effectively controlled disease in most dogs with MUO. Response rate was lower for dogs with spinal cord MUO or presumptive NME.