An overview of multiple myeloma in dogs and cats - Veterinary Medicine
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An overview of multiple myeloma in dogs and cats
These plasma cell tumors originate in the bone marrow and can cause a variety of effects, from hemorrhaging to spinal cord compression.


VETERINARY MEDICINE


TREATMENT

When treating patients with multiple myeloma, it is necessary not only to treat the underlying neoplasia but also the secondary conditions associated with the disease.

Fluid therapy

Intravenous fluid therapy is often needed initially to correct dehydration, improve cardiovascular status, and manage hypercalcemia and azotemia. Treatment with isotonic saline solution is preferred over other crystalloid replacement fluids in the initial management of hypercalcemic patients.

Antibiotics

Antibiotic therapy may be needed to treat concurrent infections, such as urinary tract infection or bacterial pyoderma, as these can progress to life-threatening infections if left untreated.

Palliative radiation

Neoplastic plasma cells are sensitive to irradiation, and radiation therapy is a highly effective palliative treatment for multiple myeloma since it can relieve discomfort and decrease the size of the mass or tumor burden.3,17,32 Indications for radiation therapy include painful bone lesions, spinal cord compression, pathologic fracture (after fracture stabilization), or a large soft tissue mass.33

Bisphosphonates

Bisphosphonates, such as pamidronate, may be useful in managing hypercalcemia as well as reducing bone pain and decreasing osteoclastic bone resorption. Evaluate blood urea nitrogen and creatinine concentrations in conjunction with urine specific gravity before using this medication since it is potentially nephrotoxic.34

The recommended dose of pamidronate is 1 to 2 mg/kg given intravenously in dogs and, anecdotally, 1 mg/kg given intravenously in cats every 21 to 28 days.35 This medication should be diluted in saline solution (amount varies based on the size of the patient) and administered as a slow infusion over two hours to minimize renal toxicosis. Bisphosphonates are an essential component of therapy for multiple myeloma in people, and their use is associated with significantly reduced skeletal-related events and improved survival in some studies.36

Analgesics

Dogs and cats with multiple myeloma may experience moderate to severe pain, and eliminating it should be a priority. Pain may be relieved by treating the underlying cancer and providing various analgesic therapies and supportive care.37,38

Plasmapheresis and other transfusions

Plasmapheresis, an extracorporeal blood purification technique, is the best immediate treatment for hyperviscosity syndrome.39 Although rarely performed in veterinary medicine, this procedure involves withdrawing anticoagulated blood, separating blood components, removing the plasma, and reinfusing the remaining components with crystalloid fluids.1,39 Packed red blood cells or platelet-rich plasma transfusions may be required if marked hemorrhage or thrombocytopenia is present, respectively.

Chemotherapy

Although a cure is unlikely, multiple myeloma can be a rewarding disease to treat since chemotherapy can greatly extend the quality and duration of life. The chemotherapy drugs most often used are alkylating agents, usually melphalan, combined with prednisone. However, eventual relapse during therapy is anticipated.

Melphalan. In dogs, the recommended treatment protocol is melphalan administered orally once daily at a dose of 0.1 mg/kg for 10 days and then 0.05 mg/kg once daily until the disease relapses or myelosuppression occurs.1 Prednisone is given concurrently at a dose of 0.5 mg/kg given orally once daily for 10 days and then 0.5 mg/kg every other day for 30 to 60 days, at which time prednisone is discontinued.1 Pulse-dose therapy with melphalan has also been described, in which melphalan, at a dose of 7 mg/m2, is given orally once daily for five consecutive days every 21 days.2 The most common side effects associated with melphalan therapy are myelosuppression and delayed thrombocytopenia. Perform a CBC every two weeks for the first two months of treatment and then monthly.

Combined melphalan and prednisone therapy can also be used in cats; however, cats appear to be much more susceptible to myelosuppression. The recommended treatment protocol is 0.1 mg/kg (or 0.5 mg total dose) melphalan given orally once daily for 10 to 14 days and then every other day until clinical improvement or leukopenia develops. A maintenance dose of 0.5 mg given every seven days is then recommended.5 Prednisone or prednisolone is given concurrently at a dose of 0.5 mg/kg orally once daily.4,5 If leukopenia develops, melphalan therapy should be discontinued until white blood cell counts return to normal; then, maintenance therapy may be attempted at the same or a lower dose.5

Other chemotherapeutics. Other chemotherapy agents used to treat multiple myeloma include chlorambucil and cyclophosphamide, either alone or in combination with melphalan.1,7 In sick myeloma patients, in which a faster response to treatment is needed, cyclophosphamide may be administered intravenously at a dosage of 200 mg/m2 once at the time that oral melphalan therapy is initiated.2 Lomustine (CCNU) has also been used in combination with prednisone to treat multiple myeloma in a cat; a partial response was obtained.40

In dogs with relapsing multiple myeloma or resistance to alkylating agents, single agent doxorubicin or the VAD (vincristine, Adriamycin [doxorubicin], and dexamethasone) protocol can be considered. This protocol combines vincristine (0.7 mg/m2 intravenously on days 8 and 15), doxorubicin (30 mg/m2 intravenously every 21 days), and dexamethasone sodium phosphate (1 mg/kg intravenously on days 1, 8, and 15); however, the reported duration of response to this protocol is only a few months.2


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Source: VETERINARY MEDICINE,
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