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Veterinary Cancer Specialists (VCS) is the oncology department for VRCC Veterinary Specialty & Emergency Hospital.

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Use of Prednisone in Canine Lymphoma: Friend or Foe?

Robyn Elmslie DVM DACVIM (Oncology)

Veterinary Cancer Specialists at VRCC


Prednisone is one of the most widely prescribed drugs in veterinary medicine, and also one of the most controversial.  Prednisone at high doses is extremely immune suppressive, making it a key drug in the treatment of a wide variety of inflammatory and immune-mediated diseases.  Prednisone can also be life saving for dogs with Addison’s disease. 

In oncology, prednisone therapy is often a key component of standard treatment protocols for dogs with newly diagnosed lymphoma.  The primary reason prednisone is so widely used in cancer is that it can bind to lymphoma cell membrane receptors and trigger rapid tumor cell death.  In addition, prednisone therapy in dogs with lymphoma exerts a number of other benefits.  For one, prednisone dramatically reduces inflammation and fever caused by malignant lymphoma cells as a consequence of prednisone induced upregulation of expression of anti-inflammatory proteins and down-regulation of expression of pro-inflammatory proteins.  Administration of prednisone also lowers blood calcium concentrations in animals with cancer-induced hypercalcemia.  This effect is mediated by decreased bone resorption of calcium, by blocking intestinal calcium reabsorption, and by increasing kidney calcium excretion.  These combined effects lead to a rapid decrease in blood levels of calcium in dogs with hypercalcemia secondary to lymphoma.  Given the therapeutic benefits of prednisone, the drug’s low cost, oral formulation and widespread availability, it is no wonder that pet owners and veterinarians both may be tempted to consider prednisone as the first line treatment for dogs newly diagnosed with lymphoma.

While prednisone sounds like a panacea for dogs with lymphoma, there are other factors to be aware of when using prednisone.  While approximately 50% of patients newly diagnosed with lymphoma will have dramatic lymph node size regression and improvement in symptoms after initiating treatment with prednisone, these benefits in many patients are short lived.  Survival times in dogs with lymphoma that are treated only with prednisone typically range from 1 -3 months, as compared to 10 to 15 months with other common multidrug protocols.  While prednisone may initially result in a partial remission of the lymphoma by killing many of the malignant cells, those cells that are inherently resistant to the prednisone will rapidly grow and mutate to become more aggressive than the original lymphoma.  This phenomenon is also known as a recurrence or relapse of the lymphoma.  This more aggressive relapsed lymphoma is often resistant to future treatment with other chemotherapy drugs, resulting in short remission and survival times for the patient.  Klein et al. (Vet Can Soc Newsletter 199115, 22-23) reported that treatment with prednisone for 2 weeks resulted in increased resistance to future treatment with chemotherapy.

Treatment with prednisone can also negatively impact the ability to make a definitive diagnosis of lymphoma.  If prednisone treatment triggers dramatic lymph node size reduction, there may not be adequate numbers of lymphoma cells to make a definitive diagnosis using standard tests such as lymph node cytology, biopsy, flow-cytometry or PCR.  The clinician and pet owner are then faced with the dilemma of deciding whether to proceed with chemotherapy without a definitive diagnosis, or to discontinue prednisone and risk recurrence of a chemotherapy-resistant form of lymphoma.  If a definitive diagnosis has been made, staging completed and tissue for immunotyping has been collected, treatment with prednisone for a few days is reasonable and not risky, particularly if the patient is not feeling well or if treatment with chemotherapy cannot be immediately initiated.

The most common side effects associated with prednisone treatment noted in our patients with lymphoma consist of increased urination and thirst, increased hunger and weight gain, and panting.  While unpleasant, these side effects are typically a reasonable trade off for the marked improvement in quality of life noted once treatment is initiated.  When prednisone is used for the treatment of lymphoma in combination with chemotherapy drugs, the prednisone treatment is generally tapered off after a few weeks and thus side effects resolve.

The most devastating side effect noted in our oncology patients on long-term prednisone therapy is muscle wasting, which can result in severe hind limb weakness, decreased stamina and perceived decrease in quality of life despite the patient achieving complete remission of the lymphoma.  Less common side effects include painful calcinosis cutis, skin infections, marked elevations in liver enzymes and poor hair coat.

At Veterinary Cancer Specialists, our guiding principle is that quality of life should come first.  The appropriateness of prednisone treatment for the individual patient must be considered along with the optimal dose and treatment duration.  With this in mind, prednisone treatment is customized for the cancer patient and can be used safely, as part of a comprehensive treatment plan.

For more information about our Oncology Team, our patients and other Oncology topics, please visit www.vetcancerspecialists.com/resources, www.facebook.com/veterinarycancerspecialists.com and www.vrcc.com/oncology.

 

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