Canine Lymphoma

by Francisco J. Alvarez-Berger DVM, DACVIM (Oncology)

Lymphoma, also known as lymphosarcoma, is a malignant tumor that originates from the lymphocytes (one type of white blood cell). This cancer commonly appears primarily in the lymph nodes; however it can affect other organs such as the spleen, liver, gastrointestinal tract, nervous system, skin, eyes and others.

Despite the fact that lymphoma is a malignant disease, most patients (approximately 90%) treated with combination chemotherapy achieve a complete clinical response (complete remission) in which there is no clinical evidence of the disease for a reasonable long period of time; in general, approximately 50% of the patients achieve more than 1 year of survival after the treatment is initiated and approximately 20% of the patients achieve more than 2 years).

In most cases, only a small sample of cells is necessary for evaluation to obtain a diagnosis. This sample is obtained by taking an aspirate using only a needle, and no sedation is needed. In some cases, when cytology does not confirm the diagnosis, a tissue biopsy for pathology is necessary to obtain a final diagnosis and to provide additional information. Additional diagnostic procedures may be required to assess the extent of the disease, including blood samples for a complete blood count and serum chemistry profile; urinalysis, abdominal ultrasound, chest X-rays and bone marrow samples.

In most cases, lymphoma is very responsive to chemotherapy when a combination of drugs is used. In the beginning of the treatment (induction therapy), patients receive weekly intravenous medications together with some others given orally at home; every time before each treatment, a complete physical exam and blood work are performed to assess if they are able to receive the medication. Once the patients complete the induction phase, all the medications may be discontinued completely as long as the tumor is in complete remission; however other patients may need to receive a maintenance treatment with oral medications or in combination with intravenous drugs. Most patients tolerate chemotherapy very well; however some patients may develop adverse effects that include loss of appetite, nausea, vomiting, diarrhea, and low blood cell counts (myelosuppression). These are usually mild and self-limiting and may be controlled completely or prevented with oral medications at home. It is very unlikely to have to hospitalize a patient due to chemotherapy complications. Most of pet owners that decide to pursue chemotherapy find the quality of life for dogs with lymphoma that received chemotherapy is very good to excellent.