Longlease Bernese Mountain Dogs Cancer Information
Lymphoma Combination drug therapy and side effects
Combination drug therapy is one option for the treatment of lymphoma. This protocol will include the drugs prednisone, vincristine, cyclophosphamide, and doxorubicin, with the possible use of L-asparaginase.
Prednisone affects the immune system, particularly targeting lymphocytes. Initial treatment will start to reduce the numbers of tumor cells in the body. While the particular side effects and their severity differ among animals, most animals show side effects when given prednisone. Your dog will likely feel thirstier than usual, and will need to be let out to urinate more frequently. Prednisone will also increase his appetite. It is important to maintain his weight at an acceptable level. If you feel inclined to give him more treats than he usually receives, consider healthier snacks such as plain rice cakes or raw vegetables. Many dogs also enjoy a few pieces of their usual kibble as a treat. He will likely beg for food more often, but you should make sure that his caloric intake remains steady. Your dog's behavior may change as well. He may pace, pant, or show other behaviors that affect his (and your) lifestyle at home. If you should decide for any reason to stop prednisone treatment after it has been administered for two weeks or more, the doses MUST be reduced gradually. It is dangerous to stop this drug suddenly; if you cannot tolerate the side effects that prednisone shows, or if you feel he is too uncomfortable with the changes, please let us develop a plan to discontinue the drug safely. Prednisone administration if used without other chemotherapy drugs may also cause your dog's tumor to develop multi-drug resistance, which could become an issue later in his treatment.
L-asparaginase works by robbing tumor cells of an essential substance they cannot make for themselves. Complications of using this drug include a potential for drug resistance with repeated treatments. Allergic reactions may also occur. The liver can be affected by l-asparaginase as well. The liver is responsible for the production of some clotting factors, and these may be temporarily reduced after the treatment. If we suspect that a patient may not be a safe candidate for l-asparaginase use, we first test for clotting disorders. Liver complications are very rare.
Vincristine targets cells that are rapidly dividing and is therefore appropriate for treatment of some lymphomas (specifically large-cell lymphomas). If vincristine escapes from the vein during administration (i.e., is extravasated), there can be local tissue irritation. Precautions are taken to ensure proper administration. Sometimes nausea, vomiting, and reduced appetite occur after this treatment, but these effects are rare with this drug and are usually readily treatable with anti-vomiting medication.
Cyclophosphamide has similar effects to vincristine. Tumor cells may develop some resistance to it after prolonged use. Side effects of cyclophosphamide include bone marrow suppression, nausea, and vomiting. Blood cell parameters are monitored closely throughout chemotherapy treatment to ensure that bone marrow suppression does not reach critical levels. If problems arise, drug doses and treatment choices are adjusted. Sterile hemorrhagic cystitis, or blood in the urine without an infection, is another potential complication, from a metabolite of cyclophosphamide administration of prednisone as part of this protocol reduces this risk by increasing your dog's drinking and urination. Nevertheless, you should increase the frequency of your dog's outside walks during the days of cyclophosphamide, to decrease the amount of time this chemical is in contact with her bladder. It also helps to increase her liquid consumption by offering her some beef or chicken bouillon during the days she is receiving this chemotherapy drug.
Doxorubicin works by affecting the DNA and RNA of tumor cells, preventing the cells from reproducing. Cardiotoxicity is the major side effect of using doxorubicin, and is related to the dose of the drug. Therefore, if the patient is experiencing side effects, we can reduce or eliminate this drug from the protocol at any time. Before doxorubicin is used we will perform an electrocardiogram and (in some patients) possibly an echocardiogram to determine the health of your dog's heart, and to help to determine whether we should proceed with doxorubicin administration. Bone marrow suppression becomes evident approximately 4 days after treatment, and reaches a peak approximately 10-14 days after treatment. Some dogs will lose their appetite, be nauseated, and (rarely) can show extreme vomiting and diarrhea from this drug, but this is not very common. If your dog vomits several times and does not hold down food or especially water, then you need to see a veterinarian immediately.
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