Oncology Update – Canine Lymphoma
Central Toronto Veterinary Referral Clinic
Kevin Finora DVM, Diplomate ACVIM (Oncology and Small Animal Internal Medicine)
Lymphoma (LSA) is the most common canine cancer. It is highly treatable and excellent responses to therapy can be seen, resulting in prolonged survival times. Here is some important information to know about canine LSA.
- Lymphoma is a disease of middle age with the average age of onset being between 6 and 9 years.
- Golden Retrievers, Rottweilers, Boxers, Bull Mastiffs, Saint Bernards, and Bassett Hounds have a higher incidence of LSA.
- The multi-centric form is most commonly seen (84%). GI, mediastinal and atypical forms are seen far less frequently (2-7%).
- No underlying cause has been reported for the development of LSA. However, a previous episode of ITP is a risk factor future development of LSA.
- Lymphoma can usually be diagnosed by cytology but some cases may require biopsy.
- Immunocytochemistry and PARR are new molecular based tests which aide in the diagnosis of LSA and can provide the immunophenotype (B vs T-cell).
- Staging determines the extent of disease in the body and includes blood work, abdominal ultrasound, chest radiographs and bone marrow aspiration.
- Prognostic factors include, immunophenotype (B-cell has better prognosis), stage (lower stage has better prognosis), healthy or ill at the time of diagnosis (Sub-stage: A; not ill at diagnosis, is better than B; ill at diagnosis).
- Hypercalcemia is a negative prognostic factor (usually associated with T-cell LSA).
- Lymphoma is a systemic disease and chemotherapy (a systemic treatment) is the treatment of choice.
- The Gold Standard for care is the CHOP Protocol. This protocol has a 90-95% remission rate and a median survival time (MST) of 13 months. With this protocol 25% of dogs will survive beyond 2 years. Cure rate is low at 1-3%.
- The CHOP protocol consists of 17 treatments given over 25 weeks. Treatments are weekly for the first 9 to 10 weeks and then every other week for the following 16 weeks.
- Other chemotherapy protocols offering MST between 90 days and 7 months exist.
- Palliation with prednisone offers a MST of 60 days. Palliative use of prednisone helps maintain quality of life.
- With no treatment, the MST is 45 days, from the day of diagnosis.
- When used alone prednisone will, after 7 to 10 days, “turn on” the P-glycoprotein (PGP) multi-drug resistance (MRD) gene, causing LSA cells to become resistant to many types of chemotherapy. This effect is not seen when prednisone is used in combination with chemotherapy agents.
- Gastrointestinal LSA, in dogs, carries a particularly poor prognosis of 14 weeks, with treatment. GI LSA is usually T-cell.
- Salmon oil, used as a dietary supplement, has demonstrated a survival advantage in some dogs with LSA being treated with chemotherapy.
- Lymphoma tends to be repeatedly chemotherapy responsive and, when LSA comes out of remission, I am usually able to re-induce remission at least 2 more times. In general subsequent remissions are half as long as previous remissions.
- Lymphoma is a cancer that should “not be given up on.” I will recommend treatment as long as the patient is doing well and treatment options exist.
Dr. Kevin Finora is a Board Certified Oncologist and Small Animal Internist who is part of the Healthcare Team at the Central Toronto Veterinary Referral Clinic. He is available for referrals and consultations Monday to Thursday (including Monday and Tuesday evenings). Please contact him with any oncology questions or concerns.
Posted by: Michael Goldstein, DVM, Diplomate ACVIM
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