Use of Prednisone in Canine Lymphoma: Friend or Foe? :: Veterinary Cancer Specialists

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.