Diffuse large B-cell lymphoma (DLBCL) is a hematopoietic tumor of B-cells. It is the most common type of non-Hodgkin lymphoma in both people and dogs, with an annual incidence of 15.5-29.9 per 100,000 people and 15-30 per 100,000 dogs.
Similarities in humans
Canine and human lymphoma (DLBCL) share many important features, including shared molecular and genetic changes, and histologic appearance. Additionally, the disease is clinically very similar between species, with an analogous disease presentation, treatment options, and response to treatment.
Differences in humans
While many of the treatment modalities used in human DLBCL are also used in dogs, there are some differences in the treatment options currently available, which can influence the way that treatment decisions are made. For example, rituximab is a monoclonal antibody that recognizes the CD20 antigen on B-cells. It is commonly used as part of a treatment regimen in people with DLBCL, however this drug does not recognize the canine CD20 protein and is therefore not included in the treatment protocols in dogs.
While any dog can develop DLBCL, several breeds are more likely to develop DLBCL in comparison to other subtypes of lymphoma; such as Rottweilers, Doberman pinchers and Cocker Spaniels. The cause of DLBCL is not well-understood, however several immunologic risk factors have been identified, including immunosuppression associated with immune-mediated disease (e.g. immune mediated thrombocytopenia) and renal transplantation. In people, a viral etiology associated with the Epstein Barr herpes virus (EBV) is described in up to 15% of DLBCL cases. While EBV has been documented in dogs, there is no confirmed retroviral involvement in the pathogenesis of canine DLBCL.
Clinical signs of DLBCL are commensurate with the stage of disease and anatomic structures involved in the disease process. The first sign of disease is often peripheral lymphadenopathy, with constitutional signs (lethargy, fever, weight loss, inappetence) becoming more prevalent in dogs with a larger burden of disease.
As in people, multi-agent chemotherapy protocols are typically used to treat dogs with DLBCL. The most commonly used regimen involves a combination of vincristine, cyclophosphamide, prednisone and doxorubicin (e.g. CHOP-based chemotherapy). The addition of rituximab, an anti-CD20 monoclonal antibody, is standard in people. While not historically available to veterinary patients, canine specific anti-CD20 monoclonal antibodies are currently under clinical investigation. Approximately 88-95% of dogs will experience a complete response to CHOP-based chemotherapy, leading to median survival times of 10-14 months in dogs with DLBCL. The breed predispositions and clinical and molecular similarities of DLBCL in people and dogs, support the continued use of dogs as a model to study biologic features of disease and investigate novel therapeutics.
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