Lymphoma is a very common cancer of dogs and is one of the most common forms of cancer in dogs that we treat here at Upstate Veterinary Specialists (UVS). It is not known why certain dogs develop lymphoma, and others do not. In some dogs, there is an underlying genetic component, and in others, there are no predisposing factors (most common). For cats, studies have shown that cats living in smoking households are 2.5 times more likely to develop lymphoma than cats living in nonsmoking households. Lymphoma usually arises in the lymphoid tissues of the body (lymph nodes, spleen, and bone marrow), though lymphoma can affect any part of the body. The most common presentation of lymphoma for dogs is enlargement of all of the lymph nodes that you can feel. The enlarged lymph nodes are usually not painful. Cats usually do not present with enlarged lymph nodes that you can feel. Often cats will have lymphoma in their gastrointestinal tract and will present to the veterinarian for vomiting, diarrhea, weight loss, or a decreased appetite. Cats and dogs can also have lymphoma in their thoracic (chest) cavity, and they may have difficulty breathing.
The type of lymphoma that dogs usually have is similar to Non-Hodgkin's lymphoma in people.
There are five stages of lymphoma (I-V), and these stages are based on what areas of the body are involved with the lymphoma. With stage I lymphoma, only one single lymph node is involved or a single lymphoid organ. Stage II lymphoma means that the lymph nodes are enlarged on one side of the diaphragm. With stage III lymphoma, all of the lymph nodes that are palpable are enlarged. If the liver and/or spleen are involved, this is classified as a stage IV. Stage V means that the lymphoma is in the blood or bone marrow or that other organ systems (such as the eye, skin, nervous system, gastrointestinal tract) are involved. Most dogs present with either stage III or IV lymphoma. This staging system is not always accurate for cats with lymphoma, for the most common presentation is gastrointestinal lymphoma, and sometimes lymphoma will be in the thoracic (chest) cavity.
The above staging system is what we utilize to determine what areas of the body are affected by the lymphoma, and this will help us to give a prognosis for your pet. There are other factors that we use when giving a prognosis for lymphoma, such as whether your pet feels sick or not. This is classified as substage. Substage A is when there are no outward signs of illness, and Substage B is when signs of illness are present. Usually cats are sick when they are diagnosed with lymphoma. We will also look at what type of lymphoma your pet has (B-cell or T-cell), for this has proven to be an important prognostic indicator. A biopsy of a lymph node may be performed to determine whether your pet has B-cell or T-cell lymphoma. Often we will not biopsy a lymph node in cats, for this typing has not proven yet to be prognostic for cats.
Diagnostics: Bloodwork (complete blood count and serum chemistry profile) and a urinalysis will be performed to determine your pet's overall health status. Chest radiographs (x-rays), abdominal radiographs, and/or an abdominal ultrasound will be performed to look for involvement of the lymphoma in certain organs. It may be requested that your pet does not eat the morning of their appointment so that certain studies can be performed with high quality results. (A better ultrasound can be performed with the stomach empty.) A fine needle aspirate may be performed of a lymph node to confirm the diagnosis of lymphoma. This is not painful for your pet. A bone marrow aspirate may be performed; this is to look for infiltration of lymphoma into the bone marrow. Your pet will be given an injection for pain before the procedure and will be under light anesthesia during the procedure. The procedure is usually performed from either the right or left front leg. Most dogs are not lame from the bone marrow aspirate, but your pet may be sleepy from the anesthesia, so please keep him or her confined to a small area and avoid steps or walking the evening of the procedure. If a biopsy of a lymph node is needed, it will be performed at the same time as the bone marrow aspirate. Your pet's oncologist will ask that you do not feed your pet the morning of the bone marrow aspirate, but water is fine up until 7 am. Eating the morning of the procedure will increase their risk of vomiting and potentially aspirating under anesthesia.
Recommendations: We will recommend that your pet be treated with systemic chemotherapy because lymphoma is always considered a systemic disease. Rarely would surgery and/or radiation therapy be utilized for lymphoma, but in certain cases, these modalities are recommended with concurrent chemotherapy. Occasionally, surgery is needed if the lymphoma is causing a blockage in the gastrointestinal tract. If surgery and/or radiation therapy are recommended, we will provide handouts to you and speak more about the specifics regarding these treatments.
Prognosis: Without any treatment, the average survival for dogs with lymphoma is 4 to 6 weeks. Approximately 50% of dogs with lymphoma will respond to prednisone (a steroid) alone, but the remission times are only 2 to 4 months with prednisone alone. Most dogs and cats with lymphoma respond very well to chemotherapy and go into a state of remission. Approximately 10% of dogs with lymphoma are cured, so a "cure" is rare. Remission is defined as the disappearance of the signs and symptoms of lymphoma in response to treatment. Our goal with chemotherapy is to obtain a remission, meaning that the lymphoma is under control and not detectable, but the disease is still present.
For Stage I-IV substage, a B-cell lymphomas the average remission time is approximately 12 to 14 months with 25% having a remission rate of 2 years. According to the literature, T-cell lymphomas have shorter remission times (usually of approximately 6 months), but we have certainly seen T-cell lymphomas and stage V lymphomas that live much longer than 6 months with a very good quality of life. Lymphoma is the most chemotherapy responsive tumor that dogs have, so we always encourage owners to treat lymphoma patients. Approximately 92% of dogs with lymphoma will go into a state of remission after the first 1 to 2 treatments. If your pet responds well to our normal chemotherapy protocol and is in a state of remission at six months, then we would stop chemotherapy and monitor closely for recurrence. When your pet comes out of remission, it will usually be the same manifestation as the original presentation (the lymph nodes will enlarge again). At that time, we may either start the original protocol again or try a "rescue" protocol, meaning that we would use chemotherapy that your pet had not previously received. Often the lymphoma will go into another state of remission. Usually the second and third remissions are not as long as the first remission. If during the original protocol your pet were to not respond to the drugs that are normally used for first line therapy for lymphoma, then a "rescue" protocol would be instituted.
In general, cats do not have as long of remission times as dogs do, but we certainly have had cats that do very well for quite some time. Prognosis is more difficult to determine for cats since the staging system and prognostic factors are not as well defined as they are for dogs. One important prognostic factor for cats is how well they respond to initial chemotherapy (if they go into a state of remission). The average remission times for cats with lymphoma with treatment are generally 7 to 9 months, but this varies tremendously from cat to cat.
In addition, your pet may be placed on oral prednisone as part of the chemotherapy protocol.
Prednisone will cause your pet to urinate more, drink more, pant more, and may increase the appetite. Please be sure that he/she has free choice water at all times and goes outside frequently to urinate. Your pet may NOT receive any aspirin or aspirin like products such as Carprofen (Rimadyl ®), Deracoxib (Deramaxx ®), Etodolac (Etogesic ®), Piroxicam (Feldane ®), Tepoxalin (Zubrin ®), Meloxicam (Metacam ®), while receiving prednisone, for the combination could cause a stomach ulcer. Most dogs will be weaned off the prednisone during the first month of chemotherapy, but it may be instituted again at some point in the protocol. Cats usually receive prednisone during the entire chemotherapy protocol.
As always, our primary goal will be to provide your pet with the best quality of life possible while receiving chemotherapy. Remember that you are the primary component of the oncology team and will always be involved in deciding what is best for your pet. We look forward to working with you and your pet here at Upstate Veterinary Specialists!
© Upstate Veterinary Specialists, 2010
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