Many Pathways to Treat Pet Cancer Means More Opportunities for Longer Survival
State-of-the-art cancer therapy involves a number of different modalities. The more conventional treatments include:
- radiation therapy
It is commonly accepted in oncology that combination therapies with multimodality protocols are more effective than single-agent therapy. We are proud of our success in this rapidly evolving area of veterinary medicine. The choice of therapy for an individual really can make a difference.
Many website links are available to discuss tumor types and to explain cancer treatments and their mechanisms and toxicities. We encourage you to expand your knowledge base using our recommended links. The following clinical cases demonstrate differences in our treatment approaches depending on the type of cancer and the individual situation.
Stories of Hope
Without a doubt, cancer is not a disease to be taken lightly. The battle against it is a difficult one and often brings with it a share of frustration. However, those who fight the battle on a daily basis often see the successes that allow us to come back the next day to fight again.
The following are only two reports of such successes. These pets arrived at VOSRC with advanced stage diagnoses and had been given grave prognoses without treatment options.
First Story: Advanced Stage Canine Lymphoma With a Novel Treatment Approach
The gold standard for treating canine lymphoma is combination chemotherapy. There are numerous protocols used in dogs, but most are based on the CHOP protocol, which includes the drugs that have been found to be most effective against lymphoma. These include vincristine, cyclophosphamide, doxorubicin, and prednisone. L-asparaginase, an anti-lymphocyte drug, is an important addition to the CHOP protocol in dogs and cats. Historically, weekly chemotherapy would be done for 6–10 months. The problem with that approach is that the majority of dogs would relapse during that time due to drug resistance, and reinduction of remission would be less than 50%. Ultimately, the cause of death in lymphoma patients is drug resistance. At VOSRC, dogs have an eight-week course of chemotherapy and drugs are stopped. Dogs can then be successfully reinduced into multiple remissions, thereby significantly improving long-term survival. Overall quality of life is improved due to fewer continuous weeks of chemotherapy.
Hector, a 2-year-old Labrador retriever, presented with lymphoma with bone marrow involvement and hypercalcemia, two negative prognostic factors for lymphoma. His prognosis was poor to grave. We initiated chemotherapy using a bone marrow purging protocol developed at VOSRC using IV continuous infusion of cytosine arabinoside for five days (Marcanato L., 2008). He then continued the standard eight-week lymphoma protocol (VCAA) used at VOSRC. Hector has been in remission for 10 years.
Second Story: Untreatable Metastatic Cancer
In many cases of metastatic cancer in veterinary oncology, a poor prognosis is given and treatment may not be offered. Aggressive cancers, however, are often the cases that will have the most dramatic response to chemotherapy. Cytotoxic drugs attack the more rapidly dividing cells, both tumor and normal cells. Rapidly growing tumors can be more sensitive to drugs.
Jaxon, a 3-year-old golden retriever, had a kidney removed due to a large tumor. Chest radiographs at the time of surgery showed no evidence of metastases. The biopsy showed an anaplastic sarcoma, a very aggressive cancer in an atypical site in a young dog—all leading to a poor prognosis. Two weeks after surgery, Jaxon came to VOSRC for a consult, at which point he was coughing. A chest radiograph showed a large lung mass. A diagnosis of metastatic sarcoma was made and chemotherapy was initiated. We used a protocol consisting of doxorubicin and dacarbazine (DTIC), initially reported for use in refractory lymphoma by Dr. Jeglum’s group at the University of Pennsylvania. This combination of drugs has become standard treatment for soft tissue sarcomas at VOSRC. Ten days after the start of treatment, Jaxon presented with lethargy. He had a low neutrophil count with fever. Follow-up chest radiographs showed complete regression of the lung mass. Within 24 hours after treatment with intravenous antibiotics and a dose of bone marrow stimulant, Jaxon was back to his young self. He went on to finish four cycles of chemotherapy. He is now a 9-year-old cancer survivor having never relapsed.