**7. Prognosis of companion animals with multiple myeloma**

Unfortunately, the prognosis of companion animals with MM is poor. The mean survival time in dogs treated with MM and treated with melphalan, cyclophosphamide and predni‐ sone is 540 days after diagnosis [27]. In dogs, negative prognostic factors include extensive bone lesions, hypercalcemia and light chain proteinuria. Renal insufficiency and poor initial response to therapy also may be associated with decreased survival times [27]. In a study of 9 cats with MM, it was found that hypercalcemia, pathologic fractures, anemia, Bence-Jones proteinuria, azotemia, persistent elevations in serum protein concentrations at 8 weeks after treatment and little or no clinical improvement were poor prognostic indicators and reflect‐ ed a more aggressive form of the disease [29]. Survival time for such cats did not exceed 14 days, with a median of 5 days. In contrast, normocalcemia, lack of azotemia, absence of pathologic fractures, no anemia, absence of Bence-Jones proteinuria and a normal serum protein 8 weeks after commencement of treatment reflected a less aggressive form with a median survival of 387 days (range between 120 and 720 days) [29].

In a study, a possible relationship between prognosis and immunoglobulin isotype was sug‐ gested in cats with MM [2], even though there are few detailed cases. Although immunoglo‐ bulin A appears to be less commonly produced than immunoglobulin G in cats, as described before, the published cases with immunoglobulin A paraproteins had visceral involvement and decreased survival time (ranging from a few days to 6 months) [12,65,267-268]. Either immunoglobulin has been associated with clinical signs of HVS, including cardiac insuffi‐ ciency, retinal hemorrhages and neurological signs [85,268]. This phenomenon relates to the size of the paraproteins and the degree of hyperglobulinemia. Since immunoglobulin A may assume a dimeric or multimeric form, it may be more commonly associated with hypervis‐ cosity than immunoglobulin G. HVS can contribute to decreased survival time in animals with MM [13,23,54,85].

The lifespan of horses diagnosed of MM usually does not exceed two years [1,3,6,8]. There is not any published case of equine MM that attempted chemotherapy and most horses are eu‐ thanized owing to the advance stage of the disease.
