The objective therapeutic goal is to achieve complete remission of the cancer. Subjectively, the goal of treatment is to restore the patient’s pain-free quality of life for as long as possible. Chemotherapy protocols are complicated and rapidly evolving. A veterinary oncologist (cancer specialist) is the best person to discuss and advise owners about treatment options for canine lymphoma.
A veterinarian normally will “stage” lymphoma to help the dog’s owner decide on a treatment protocol. The stages of lymphoma in dogs basically are as follows:
- Stage I - only one lymph node (or lymphoid tissue in one organ) is involved.
- Stage II – multiple lymph nodes or a chain of lymph nodes in a localized area are involved.
- Stage III – Widespread, generalized lymph node involvement; most or all peripheral lymph nodes are affected.
- Stage IV - any or none of the above, plus liver and/or spleen involvement.
- Stage V - any or none of the above, with bone marrow involvement, blood involvement or involvement of any non-lymphoid organ.
Each stage can further be classified into substage A (the dog has no observable symptoms of illness), or substage B (the dog is showing signs of illness, such as loss of appetite, lethargy, weight loss, or the like).
Treatment Options for Lymphoma in Dogs
Chemotherapy is defined as the treatment of illness or disease using chemical agents. Some chemotherapeutic medications can be given orally, while others must be given intravenously (IV) on an inpatient basis. Moreover, chemotherapeutic protocols may involve administration of only one drug or a combination of drugs. Multi-agent chemotherapy typically results in better remission rates and a more rewarding overall outcome than does single agent therapy. Chemotherapy targets rapidly-dividing cells.
Treatment protocols are rapidly changing, and chemotherapeutic drugs can have severe and potentially fatal side effects. Current protocols for treating canine multicentric lymphoma can involve use of a number of different drugs, including cyclophosphamide, vincristine, prednisone, L-asparaginase and doxorubicin, among other. Other chemotherapy drugs, such as chlorambucil, lomustine, cytosine arabinoside and mitoxantrone, are sometimes used in the treatment of lymphoma as well, either singly or in addition to other drugs. It is extremely important to closely monitor white blood cell counts and remission status throughout the course of chemotherapy.
While used much less commonly than chemotherapy, radiation therapy is being explored to treat lymphoma in combination with drug treatment. Early research suggests that certain chemotherapeutic protocols, used in combination with radiation, improve remission rates and extend the disease-free interval in dogs with multicentric malignant lymphoma.
Dogs with lymphoma isolated to a single or several lymph nodes, and those with focal gastrointestinal lymphoma, may be able to be treated successfully by surgical removal of the lymph node or mass followed by chemotherapy and/or radiation. Chemotherapy with or without radiation treatment has improved survival times in dogs suffering from mediastinal lymphoma. Cutaneous lymphoma can be treated with single or multi-agent chemotherapy, although the disease tends to become refractory to treatment and the results are much less rewarding.
Stem cell transplantation is commonly used to treat people with lymphoma and is another possible treatment option for dogs. In fact, much of the basic research on stem cell transplantation was generated from dogs. When cost is a restricting factor, steroid drugs such as prednisone can be prescribed to help alleviate the symptoms of lymphoma, although this will not significantly affect the survival rate. Prednisone may also cause the cancer to become resistant to other chemotherapeutic agents and typically is only used if more aggressive treatment is not an option.
Some cancers do not respond particularly well to chemotherapy. Fortunately, canine lymphoma – especially the common multicentric form – usually does. Radiation treatment is available for some types of cancer as well and is being used increasingly in conjunction with chemotherapy, with the hope of improving remission rates. During any chemotherapy treatments, the patient will need frequent blood tests and monitoring to be sure that the treatment is not adversely affecting his or her organs or overall health. Of course, in pets and in people, there can be a number of unpleasant side effects from chemotherapy and/or radiation treatment, including severe gastrointestinal upset, allergic reactions and hair loss, among others.
Current treatment protocols can help to extend a dog’s life after a diagnosis of lymphoma. Dogs with lower stage lymphoma have a better prognosis than those with higher stage disease. Unfortunately, lymphoma is almost always progressive and, ultimately, fatal. Treatment of lymphoma rarely cures the disease. Instead, it hopefully will make the patient feel a bit better, and live a bit longer, with a significantly improved quality of life if remission is achieved.