Multiple Myeloma in Dogs

What Is Multiple Myeloma in Dogs?

Multiple myeloma is a rare type of blood cancer that can develop in plasma cells, which are white blood cells that make antibodies to help your dog’s body fight off germs that can cause them to get sick. Plasma cells are found in bone marrow, the spongy material in the center of your dog’s bones.

Plasma cells that become cancerous make abnormal antibodies that can hurt instead of help your dog. These cancerous plasma cells build up faster than healthy plasma cells and eventually become the main type of plasma in your dog’s bone marrow. Multiple myeloma typically starts in multiple places within the bone marrow.

The abnormal antibodies coming from cancerous plasma cells can make their way to other organs in the body such as the kidneys. This can cause these organs to not function properly.

Symptoms of Multiple Myeloma in Dogs

It can take years for symptoms of multiple myeloma to appear, but your dog may experience:

• Signs of pain, such as more sensitivity to touch

• Lameness

• Weight loss

• Abnormally low numbers of white blood cells and blood platelets

• Abnormally high levels of calcium in the blood

• Bone damage from the breaking down of bone cells, causing the spinal cord to compress and bones to break most often in the spine, pelvis, ribs, skull, or areas of the leg closest to the trunk of your dog’s body

• Kidney failure

• Heart disease

Causes of Multiple Myeloma in Dogs

There is no single known cause for multiple myeloma. Exposure to chemicals, constant activation of the immune system, illness from a viral infection, and genetics are all suspected to play a role.

The Giant Schnauzer, Labrador, Golden Retriever, and German Shepherd breeds have higher rates of multiple myeloma, but it is not clear why.

Gender does not seem to be a risk factor for multiple myeloma, although neutered females and intact males are overrepresented in some case studies.

As with most other cancers, older dogs are more likely to be affected by the disease. The average age of diagnosis for multiple myeloma is eight to nine years old.

How Veterinarians Diagnose Multiple Myeloma in Dogs

Multiple myeloma is very rare and makes up less than 1% of all cancers in dogs, so it may not be the first suspected cause of your dog’s symptoms.

Multiple myeloma has four classic criteria that can be tested to confirm its presence. At least two must be met for a diagnosis to be made.

Your dog’s vet will do several different tests to find which, if any, of these signs are found:

• Visualizing bone damage–Your veterinarian may use X-rays or computed tomography (CT scan) to see your dog’s bones. Bones with a “patchy” appearance may be damaged, which is a common clinical sign of multiple myeloma.
• Finding the number of plasma cells–Your veterinarian may take a sample of cells or a piece of tissue from your dog’s bone marrow to find out the relative amount of plasma cells. Multiple myeloma may be present if more than 20% of the cells in your dog’s bone marrow are plasma cells.
• Checking levels of globulin in blood–Your veterinarian may do blood work to find the levels of globulin present in your dog’s blood. Globulin is a type of protein, and there is a lot more of it when a dog has multiple myeloma.
• Examining the amount of Bence-Jones proteins in urine–Your veterinarian may analyze your dog’s urine to figure out the level of Bence-Jones proteins present. Bence-Jones proteins are a type of antibody. High levels of these in urine is a sign of multiple myeloma.

Multiple myeloma does not result in a solid tumor mass because it is a blood cancer found throughout the body’s bloodstream and bone marrow. This can make staging for multiple myeloma (the process of figuring out how much cancer is in your dog’s body and where) more difficult. Regardless, staging may be a helpful indicator of how far your dog’s cancer has progressed.

Multiple myeloma can go unnoticed for a number of years before clinical signs can be seen, so it's hard to tell how long your dog has been living with the disease. However, your veterinarian may be able to estimate how severe your dog’s multiple myeloma is by comparing relative levels of abnormal antibodies and proteins in their blood or urine.

Treatment of Multiple Myeloma in Dogs

Most dogs with multiple myeloma tolerate treatment well and can greatly benefit from it.

Chemotherapy is often the first choice of treatment. Approximately 80 to 95% of dogs diagnosed with multiple myeloma benefit from chemotherapy within three to six weeks.

 Oral chemotherapy medications that may be prescribed include:

• Melphalan (most commonly used with a corticosteroid called prednisone)
• Chlorambucil and cyclophosphamide (may be prescribed either alone or together)
• Doxorubicin (most often used for relapses and may be used with another chemotherapy drug, vincristine)

Radiation can also help to treat multiple myeloma and ease bone pain to make your dog more comfortable.

Fluid therapy may be suggested to make sure your dog is hydrated and has the right level of electrolytes. This can be especially helpful for dogs with kidney failure due to multiple myeloma.

Anti-inflammatory medicines, such as corticosteroids like prednisone or dexamethasone, may be prescribed to help reduce swelling. Inflammation is an important natural reaction to injury and infection in the body, but too much inflammation can be painful and can damage healthy cells. Furosemide is a medication that can help reduce swelling. It can be particularly helpful for dogs with kidney failure and heart disease due to their multiple myeloma.

Bisphosphonates, such as pamidronate, may be incorporated into your dog’s treatment plan as well. These can be useful for stopping the breakdown of bone cells, which helps to decrease the level of calcium in your dog’s blood, ultimately improving their bone condition and relieving pain.

Recovery and Management of Multiple Myeloma in Dogs

Multiple myeloma is rarely cured, and dogs who achieve remission are expected to relapse. Fortunately, multiple myeloma is manageable so long as your dog is checked by their veterinarian often. This means that regularly scheduled blood tests and examinations by a veterinarian will be needed.

Doing things that help to keep your dog otherwise healthy and comfortable while they are living with the disease can help. For example, your dog’s veterinarian may suggest feeding them a well-balanced diet low in carbohydrates and high in cancer-fighting compounds like omega-3 fatty acids, giving them a daily multivitamin to ensure their nutritional needs are met, or administering medication as prescribed to control their pain levels.

Talk to your veterinarian to help you figure out which practices may be best for your dog.