Medical Oncology: Canine Low-grade Lymphoma/ Chronic Lymphocytic Leukemia
What Is Low-grade Lymphoma?
Lymphoma is a cancer of lymphocytes. Lymphocytes are part of the immune system.
Low-grade lymphoma is also called small cell lymphoma or lymphocytic lymphoma. The
most common locations for low-grade lymphoma are lymph nodes and the spleen.
What Is Chronic Lymphocytic Leukemia?
Chronic lymphocytic leukemia (CLL) is also a cancer of lymphocytes. The difference is
that most of the cancerous cells are usually found in the blood rather than in lymph nodes
or the spleen.
What Are The Clinical Signs?
Many dogs with either low-grade lymphoma or CLL have no clinical signs. They are
diagnosed during a routine vet exam or with regular bloodwork.
Dogs with either disease could show lymph node enlargement, weight loss, vomiting,
diarrhea, and decreased appetite. Signs usually develop slowly, over months to even
years.
Dogs with low-grade lymphoma are at risk for a specific skin parasite (Demodex mites).
These dogs have fur loss, reddened and/or flaky skin, and may be itchy.
Dogs with CLL can have weakness related to a low red blood cell count (anemia),
bruising due to a low platelet count, and/or illness due to a low neutrophil (type of white
blood cell) count.
WHAT DIAGNOSTICS ARE PERFORMED?
The accurate diagnosis of low-grade lymphoma/CLL requires a combination of tests.
Physical exam: Examines for enlarged lymph nodes and/or other abnormalities.
Complete blood count (CBC): Looks for abnormalities in the cells in the bloodstream.
Dogs with CLL usually have markedly increased numbers of lymphocytes in their blood.
But some dogs with low-grade lymphoma show this as well.
Chemistry panel: Looks at the function of internal organs and checks the patient’s
electrolyte status.
Thoracic radiographs (x-rays): Looks for enlarged lymph nodes in the chest and
evaluates the heart and lungs for abnormalities.
Abdominal ultrasound: Looks for enlarged lymph nodes in the abdomen and evaluates
the liver and spleen for involvement. Sometimes samples of these organs are taken with a
small needle to check for cancer cells.
Bone marrow aspirate: Looks for signs of bone marrow cancer. Recommended for
cases where there are abnormal findings on the CBC.
Lymph node biopsy: Confirms the diagnosis of low-grade lymphoma (versus other
forms of lymphoma). Involves the removal of an entire lymph node.
Flow cytometry/PARR: Performed on blood or bone marrow samples to confirm the
diagnosis of CLL (versus other forms of leukemia). They can also be done on samples
from lymph nodes or other organs to confirm a diagnosis of low-grade lymphoma (versus
other forms of lymphoma).
Treatment Options
Not all cases of low-grade lymphoma/CLL require treatment. Monitoring with monthly
physical exams and CBCs are appropriate for dogs with no clinical signs and lymphocyte
counts under 60,000 cells/uL. Treatment is started when lymphocyte counts are higher
than 60,000 cells/uL, patients become sick, there is evidence of decreased counts of other
cells in the blood, and/or there is internal organ or lymph node enlargement.
Low-grade lymphoma/CLL are treated the same way, with two oral medications:
prednisone (steroid) and chlorambucil (chemotherapy), which are given at home.
Treatment is chronic (years to lifelong). In the beginning, dogs are monitored monthly
with exams and lab work. If a positive response is seen (lymph nodes decrease in size,
number of cancer cells decreases in bloodstream, etc.), rechecks are spaced out every 2-3
months.
Surgical removal of the spleen or a solitary tumor is an option for some dogs with low-
grade lymphoma.
Prognosis
The median prognosis for low-grade lymphoma/CLL is 2 years with treatment. Rarely,
either disease can undergo ‘blast transformation. This is a rapidly progressive condition.
There is no way to predict which cases will have this complication. The prognosis for
those patients is poor.
What Are The Side Effects?
Prednisolone and chlorambucil are well-tolerated. The biggest challenge for owners is
being able to give the medications to their dogs. We will assist you in ways to be
successful in doing so.
How Do I Prepare
We understand this is a difficult time and we are here to support you and your pet by
providing the options and care necessary. Selecting a therapy is not binding and can be
adjusted to you and your pet’s needs. You will be updated on your pet’s response to
treatment and plan.
Getting Started
Once you have determined the best therapeutic option for your pet, you will work with
our oncology team to develop an appointment plan.
Scheduling: Patients undergoing chemotherapy treatments must have a scheduled
appointment before arrival:
- Schedule your appointments at reception upon check out
- Drop-offs are requested between 7:30-8:30 am
- No discharges are done between 2:30 pm- 3:30 pm as our oncology team is in rounds