Lymphosarcoma (LSA) can affect any breed or age of dog; however, it is more common in middle-aged or older dogs, according to Washington State University College of Veterinary Medicine (WSUCVM). The cause is unknown. Chemotherapy may help prolong a dog's life. Although some dogs live several years, LSA is not generally curable. Remission is often attainable more than once. The cost of chemotherapy depends on the drugs used, the size of the dog and protocols used.
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Lymphoma
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The choice of chemotherapy depends on the dog's health and lymphoma progression. LSA, commonly found in the lymph nodes, can be anywhere including the liver, spleen, bone marrow, skin and organs, according to WSUCVM. Symptoms depend on where the cancer is located and whether the growth is interfering with normal function. In order to determine chemotherapy protocol, the veterinarian will determine the stage of cancer according to size, number of sites and organ involvement. The substages of lymphoma, "a" or "b," are whether the dog acts healthy or is sick. Dogs who are sick at onset of chemotherapy have a shorter survival time than those who seem well.
Chemotherapy
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Chemotherapy drugs work to kill cancer cells. Cancer cells divide at a very rapid rate. According to College of Veterinary Medicine at the University of Illinois (CVMUI), the drugs interfere with cells that divide rapidly and help kill them. Chemotherapy also damages and kills healthy cells that divide rapidly, especially in the gastrointestinal tract and bone marrow. Administration of chemotherapy drugs is done orally, intravenously (IV) or through injections under the skin or in the muscle. Chemotherapy may be the only treatment or it may be combined with surgery or radiation. When given by IV, the dog usually is required to stay at the hospital for several hours.
Initial
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Most chemotherapy protocols involve the use of several drugs rotated or combined and administered over various amounts of time. The drugs generally used include L-asparaginase, vincristine, prednisone, cyclophosphamide and doxorubicin, according to WSUCVM. Other drugs, such as adriamycin and Oncovin, are also used. Common protocols are the Wisconsin, COP and COPA (named for the drugs used) protocols. Dog response or side effects may require changing protocols or adjusting dosages or schedules.
Rescue
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Most dogs can achieve remission and regain it after loss at least once or twice, according to Francisco Alvarez Berger, M.V.Z., at the Department of Veterinary Clinical Sciences, Ohio State University. However, when the dog cannot regain remission with regular chemotherapy, rescue protocols are used. Rescue protocols require individualization depending on which treatments the dog has become resistant to, according to Berger. Common drugs include lomustin and asparaginase or the addition of drugs to a previous protocol.
Side Effects and Prognosis
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Survival time is about six weeks without chemotherapy and six to 10 months average with chemotherapy, according to Gregory K. Ogilvie, D.V.M., D.A.C.V.I.M., CVS Animal Care Cancer Center. Dogs treated with just prednisone live about two months. Many dogs live longer with chemotherapy but some, especially those who experience serious side effects, may not ever attain remission. Serious side effects affecting the bone marrow may reduce survival time as it can halt chemotherapy. Gastrointestinal side effects, according to CVMUI, generally do not prevent continuation of chemotherapy. Other side effects, such as hair loss or injection site reaction, are minimal.
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