Lymphoma is one of the most common cancers in dogs. It originates from a mutation and proliferation of a type of white blood cell called a lymphocyte. By the time of diagnosis, this cancer typically affects multiple different areas of the body at once. For this reason, it is not often a disease that is treated with surgery. Rather, we use chemotherapy to manage this cancer.
Chemotherapy is administered with the primary goal of fighting cancer while maintaining a very good quality of life for the pet. Our drugs are dosed with this goal in mind.
There are over 40 different kinds of lymphoma diagnosed in our dogs. Definitive diagnosis of this cancer type requires a biopsy tissue sample often obtained with a small needle-core biopsy that can be done under heavy sedation and pain medications.
Alternatively, most oncologists feel comfortable diagnosing high-grade, lymphoma based on a fine-needle aspirate, cytology and potentially further molecular diagnostics. Although this will not give you a definitive diagnosis, the vast majority of cases will provide very high-suspicion of lymphoma.
There are two main categories of high-grade lymphoma, B-cell or T-cell (immunophenotype) lymphoma, which have prognostic significance. For example, although we still extend pet’s lives in many cases, T-cell lymphoma patients often do not live as long with treatment as dogs diagnosed with B-cell lymphoma. Also, treatment decisions in the future may differ depending on the immunophenotype.
Treatment and Prognosis:
The treatment of choice for most dogs with lymphoma is a multi-agent chemotherapy protocol (standard of care), which takes advantage of 4 drugs, vincristine, cyclophosphamide, doxorubicin and prednisone. Deviations from the initial treatment plan are possible since it is tailored for the individual pet to prevent chemotherapy-related side effects while still being as efficacious as possible against the cancer. For dogs diagnosed with B-cell lymphoma, with this chemotherapy protocol, 80-90% of dogs go into a complete remission (meaning that your pet’s cancer is no longer detectable) and the median survival time is approximately 1 year from the time of diagnosis. This means that 50% of animals will live longer than 1 year and 50% of animals will have a shorter survival time.
Less intensive and less expensive treatment options are available. Although dogs still experience a good quality of life, survival times obtained with these protocols are not as long as with the standard of care, the multi-agent protocol.
Finally, if chemotherapy is not used to treat dogs with lymphoma, we can use a steroid called prednisone to manage the disease. Prednisone has anti-cancer effects and can help dogs with lymphoma feel better for some period of time. Typically, the survival time for dogs with lymphoma receiving prednisone alone (i.e. without chemotherapy) is 1-3 months. Because lymphoma tends to be a quickly progressive cancer, if left untreated the expected survival time is approximately 4-6 weeks.
NOTE: If you choose to treat your pet with prednisone alone, it is important to realize that while chemotherapy is still an option (if you choose to pursue it in the future), the prednisone may make the chemotherapy less successful. If prednisone is started several weeks before chemotherapy is started, it will cause the cancer cells to become more resistant to chemotherapy. However, most oncologists agree that giving prednisone for several days before starting chemotherapy should not have any detrimental effects.