Canine Lymphoma: A Quick Snapshot
Canine Lymphoma: A Quick Snapshot
Today, like many days I spend in AMC’s Cancer Institute I saw a dog patient diagnosed just a few days ago with lymphoma. What appears below is a summary of my conversation with the dog’s family about lymphoma and the options for treatment of their beloved companion.
What is Lymphoma?
Lymphoma is cancer of the lymph nodes or other lymphoid tissue such as the spleen or tonsil. In dogs (and also humans) it is not a single disease, but is probably more than 20 different diseases; each of the 20 or so forms of lymphoma behaves somewhat differently and the prognosis varies between types. In dogs with lymphoma, we most commonly see enlarged lymph nodes on the outside of the body and using x-rays or ultrasound, see enlarged internal lymph nodes as well. When viewed using a microscope, the cells in a normal lymph node are composed of a variety of different sized cells called lymphocytes. Lymphocytes in enlarged lymph nodes (shown in the photomicrograph) typically appear much larger in diameter than the cells normally inhabiting the lymph nodes. Lymphocytes in lymphoma demonstrate less variation in their size than in a normal lymph node. If special testing is performed, the lymphocytes can be identified as either B or T cells. This differentiation is an important predictor of outcome.
How is Lymphoma Treated?
Three major types of treatments underlie all cancer therapy: surgery, radiation therapy and chemotherapy. Since lymphoma is widespread throughout the body at the time of diagnosis, surgery is not generally used for treatment as removal of all the lymph tissue in the body is impossible. Surgery may be recommended to obtain a biopsy for diagnosis. Radiation therapy can be used in select cases of canine lymphoma, but chemotherapy forms the mainstay of canine lymphoma treatment.
Multiple Lymphoma Protocols
In my office file drawers, I have a big fat folder of articles describing various chemotherapy protocols for the treatment of lymphoma. Many of them are simply a riff on a theme. In my opinion, there are three basic options for treatment of canine lymphoma:
- Steroids, glucocorticoids, cortisone, and prednisone are all names for the same type of drug. In lymphoma, steroids kill the cancer cells but are not ”traditional” chemotherapy agents.
- Treatment with a single chemotherapy drug, most commonly doxorubicin (Adriamycin®), although others can be used.
- Using multiple chemotherapy drugs known to be effective against lymphoma and combining them into a rotational schedule which minimizes toxicity and maximizes efficacy.
How Long Will My Dog With Lymphoma Live?
The quick answer to this question is, ‘it depends,’ and I realize that answer is in no way helpful. The contingencies listed below are general rules, but cannot be used to predict how an individual dog will respond to treatment. First, dogs treated with chemotherapy live longer than untreated dogs. The most common form of lymphoma seen in dogs progresses rapidly and if untreated, the average survival time is about two months. With treatment, these dogs often survive a year or more. Some lymphomas are considered indolent or slowly progressive. Dogs with this form of lymphoma may survive years without any treatment; however, indolent lymphoma is quite rare. Dogs showing clinical signs related to their lymphoma have a shorter survival than dogs who still are feeling well. Dogs diagnosed with T cell lymphoma do not respond to chemotherapy for as long a time as dogs with B cell lymphoma.
Helpful Hints About Lymphoma
- Lymph nodes enlarged due to lymphoma are most commonly painless swellings under the chin, in front of the shoulders, behind the knees.
- A quick needle aspirate can be used to diagnose lymphoma, but occasionally a biopsy is recommended to provide additional information about the specific type of lymphoma.
- In a survey of dog owners who chose to treat their dog’s lymphoma with multiagent chemotherapy, 92% had no regrets about their decision and 68% felt their dog’s quality of life was the same as before treatment with chemotherapy.
Photo: A microscopic view of lymphoma cells in a lymph node. Photo courtesy of Dr. Jamie Haddad, IDEXX Laboratories