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Multiple Myeloma in Dogs

What Is Multiple Myeloma in Dogs?

Multiple myeloma in dogs is a rare form of blood cancer that originates in plasma cells, specialized white blood cells responsible for producing antibodies that defend the body against harmful pathogens. These plasma cells reside in the bone marrow, the inner, spongy tissue within your dog’s bones.

When plasma cells undergo malignant transformation, they generate abnormal antibodies that are detrimental rather than beneficial to your dog’s health. The proliferation of these cancerous plasma cells outpaces that of healthy plasma cells, eventually dominating the bone marrow. Multiple myeloma typically manifests in several locations within the bone marrow.

The aberrant antibodies produced by cancerous plasma cells can travel to various organs, such as the kidneys, where they interfere with normal organ function, leading to dysfunction.

Symptoms

Symptoms of multiple myeloma in dogs may not become evident for several years, but your dog might exhibit the following:

  • Increased sensitivity to touch, indicating signs of pain.
  • Limping or lameness.
  • Weight loss.
  • Decreased levels of white blood cells and blood platelets.
  • Elevated levels of calcium in the bloodstream.
  • Bone deterioration resulting from the breakdown of bone cells, potentially leading to spinal cord compression and fractures, particularly in the spine, pelvis, ribs, skull, or proximal leg regions.
  • Kidney malfunction.
  • Heart disease.

Causes

The exact cause of multiple myeloma in dogs remains unknown. Suspected factors include exposure to chemicals, prolonged activation of the immune system, viral infections, and genetic predispositions.

Certain breeds such as the Giant Schnauzer, Labrador, Golden Retriever, and German Shepherd have higher incidences of multiple myeloma, though the reasons behind this correlation are unclear. Gender doesn’t appear to be a significant risk factor for multiple myeloma, although some case studies show a higher representation of neutered females and intact males.

Similar to many other types of cancer, older dogs are more susceptible to developing multiple myeloma, with the average age of diagnosis typically ranging from eight to nine years old.

Diagnosis

Diagnosing multiple myeloma in dogs can be challenging due to its rarity, accounting for less than 1% of all canine cancers. Consequently, it might not be the initial suspicion when your dog exhibits symptoms.

To confirm multiple myeloma, veterinarians rely on four classic criteria, with at least two needing to be met for a diagnosis:

  • Visualizing bone damage: Your veterinarian may utilize X-rays or computed tomography (CT scan) to assess your dog’s bones. Patchy appearances on imaging may indicate bone damage, a common indication of multiple myeloma.
  • Determining the number of plasma cells: Samples of cells or bone marrow tissue are examined to assess the relative proportion of plasma cells. If over 20% of cells in the bone marrow are plasma cells, multiple myeloma may be suspected.
  • Checking globulin levels in blood: Blood tests are conducted to measure globulin levels, a type of protein. Elevated levels often indicate the presence of multiple myeloma.
  • Analyzing Bence-Jones proteins in urine: Urine analysis helps determine the concentration of Bence-Jones proteins, a type of antibody. High levels in urine suggest multiple myeloma.

Given that multiple myeloma is a blood cancer distributed throughout the bloodstream and bone marrow, staging can be challenging. However, staging aids in understanding the extent of cancer spread in your dog’s body.

Multiple myeloma can remain asymptomatic for years, making it difficult to ascertain its duration. Nonetheless, veterinarians can estimate the severity of the disease by comparing levels of abnormal antibodies and proteins in the blood or urine.

Treatment

Treatment for multiple myeloma in dogs is generally well-tolerated and can significantly improve their quality of life.

Chemotherapy is typically the primary treatment option, offering benefits to approximately 80 to 95% of dogs within three to six weeks of initiation. Common oral chemotherapy medications include:

  • Melphalan, often administered alongside the corticosteroid prednisone.
  • Chlorambucil and cyclophosphamide, prescribed either individually or in combination.
  • Doxorubicin, primarily used for relapses and sometimes combined with another chemotherapy drug, vincristine.

Radiation therapy can also be employed to manage multiple myeloma and alleviate bone pain, enhancing your dog’s comfort.

Fluid therapy may be recommended to ensure proper hydration and electrolyte balance, particularly beneficial for dogs experiencing kidney failure due to multiple myeloma.

Anti-inflammatory medications like corticosteroids (e.g., prednisone or dexamethasone) may be prescribed to alleviate swelling. While inflammation is a natural response to injury and infection, excessive inflammation can be painful and harmful to healthy cells. Furosemide, a medication that reduces swelling, can be particularly beneficial for dogs with kidney failure and heart disease resulting from multiple myeloma.

Bisphosphonates such as pamidronate may also be integrated into your dog’s treatment regimen. These drugs help halt the breakdown of bone cells, lowering the calcium levels in your dog’s blood and improving bone health while alleviating pain.

Living and Management

Recovery from multiple myeloma in dogs is rare, and even those achieving remission are prone to relapse. However, effective management strategies can ensure a good quality of life for your dog. Regular veterinary check-ups are essential, involving scheduled blood tests and examinations to monitor their condition closely.

Maintaining your dog’s overall health and comfort is crucial while living with the disease. Your veterinarian may recommend:

  • Providing a well-balanced diet low in carbohydrates and rich in cancer-fighting compounds such as omega-3 fatty acids.
  • Supplementing their diet with a daily multivitamin to meet their nutritional requirements.
  • Administering prescribed medications to manage pain levels effectively.

Consulting with your veterinarian will help determine the best practices tailored to your dog’s specific needs.

Multiple Myeloma in Dogs FAQs

How long can a dog live with multiple myeloma?

Dogs diagnosed with multiple myeloma can live for 18 months or more with appropriate treatment. Among the treatment options, chemotherapy tends to yield the longest median survival times.

How common is it for dogs to reach remission with multiple myeloma?

In a research study involving 60 dogs treated with the chemotherapy drug melphalan and the corticosteroid drug prednisone for multiple myeloma, findings showed that 43% experienced complete remission, 49% achieved partial remission, and 8% showed no response to the treatment.

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