History An 8-year-old neutered male Greyhound was evaluated at the Tufts Animal Behavior Service for intermittent episodes of extreme anxiety. The first anxiety attack occurred in late October of 2008 and lasted for 3 days. Physical examination, CBC and serum biochemistry analysis performed by the referring veterinarian were within reference limits.
Every veterinary student knows that lymphoma is the most common hematopoietic neoplasm in dogs and cats. However, we are now recognizing that lymphoma isn’t a single clinical entity. Rather, it is a collection of neoplastic disorders triggered by a myriad of genetic mutations and epigenetic factors that culminate in uncontrolled proliferation of lymphocytes. Multi-institutional collaborative efforts are underway to illuminate the molecular fingerprints of canine and feline lymphomas that will allow for better understanding of the biology of lymphoma as well as improving treatment strategies and outcomes. These benefits are likely to extend across species – even to humans as the field of comparative oncology grows.
Figure 1. Lymphoma in dogs typically presents as generalized peripheral lymphadenopathy. Mandibular swelling due to lymph node enlargement, as shown here, often is a sign that leads clients to seek evaluation.
High-Dose Cyclophosphamide Holds Promise for Dogs with Lymphoma
For decades, the cornerstone of treatment for dogs with lymphoma has been chemotherapy employing five drugs: cyclophosphamide, doxorubicin, vincristine, L-asparaginase and prednisone. Efforts to optimize these protocols by adjusting the doses and scheduling of drugs have not yielded significant improvement in remission rates or survival times. In addition, the realization that discontinuous short chemotherapy protocols are as effective as traditional long protocols that include a lengthy maintenance phase has provided the opportunity to search for novel therapies to combat lymphoma before overt chemotherapy resistance develops.
Alternative modalities that have been studied include radiation therapy, chemotherapy agents traditionally reserved for rescue therapy, monoclonal antibodies, dose-intensified chemotherapy and bone marrow transplantation. These approaches have yielded variable results, and some promising findings are under continued investigation. Continue reading →