Cyclical 10-day dosing of melphalan for canine multiple myeloma

Canine multiple myeloma (MM) is typically treated with melphalan chemotherapy. A protocol with repeated 10-day cyclical dosing of melphalan has been used at our institution but has not been described in the literature. Our objectives were to describe the outcome and adverse events of this protocol in a retrospective case series. We hypothesised the cyclical 10-day protocol would have similar outcomes compared to other reported chemotherapy protocols. Dogs diagnosed with MM that received melphalan treatment at Cornell University Hospital for Animals were identified through a database search. Records were retrospectively reviewed. Seventeen dogs met inclusion criteria. Lethargy was the most common presenting complaint. The median duration of clinical signs was 53 days (range, 2-150 days). Seventeen dogs had hyperglobulinemia with 16/17 having monoclonal gammopathies. Sixteen dogs had bone marrow aspiration and cytology performed at initial diagnosis and plasmacytosis was diagnosed in all. Based on serum globulin concentrations, 10 of 17 dogs (59%) achieved complete response (CR), and 3 dogs (18%) achieved partial response (PR), for an overall response rate of 76%. The median overall survival time was 512 days (range, 39-1065). Retinal detachment (n = 3) and maximum response of CR/PR (n = 13) were associated with overall survival on multivariate analysis (p = .045 and .046, respectively). Adverse events were minimal with diarrhoea being the most reported (n = 6). This cyclical 10-day protocol was better-tolerated with fewer adverse events than with other reported chemotherapy protocols, but response rate was also lower, likely due to a lower dosing intensity.