Evaluation of a Novel Tumor Vaccine in Dogs with Hemangiosarcoma

Abstract

Background: Hemangiosarcoma (HSA) is a highly metastatic and often rapidly fatal tumor of dogs. At present, adjuvant chemotherapy is the only proven effective treatment for dogs with HSA, though the benefits from chemotherapy are modest. Administration of immunotherapy together with chemotherapy has also been reported to improve survival in dogs with HSA. Therefore, we evaluated safety and immunologic responses to a novel tumor vaccine administered together with doxorubicin chemotherapy in dogs with different stages of HSA. Hypothesis: That tumor vaccination could be safely and effectively combined with doxorubicin chemotherapy for treatment of dogs with HSA. Animals: Twenty‐eight dogs with various stages of HSA were enrolled in the study. Methods: The HSA vaccine was prepared with lysates of allogeneic canine HSA cell lines mixed with an adjuvant composed of liposome‐DNA complexes. Dogs received a series of 8 immunizations administered over a 22‐week period, and most also received chemotherapy. Clinical adverse effects were noted, immune responses were measured by enzyme‐linked immunosorbent assay (ELISA) and flow cytometry, and survival times were calculated. Results: The most common adverse effects observed in vaccinated dogs also treated with doxorubicin chemotherapy were diarrhea and anorexia. Vaccinated dogs were found to mount strong humoral immune responses against a control antigen and, most dogs also mounted antibody responses against canine HSA cells. Thirteen dogs with stage II splenic HSA that received the tumor vaccine plus doxorubicin chemotherapy had an overall median survival time of 182 days. Conclusions: We conclude that an allogeneic tumor lysate vaccine is safe in dogs with HSA and can elicit humoral immune responses in dogs that are receiving concurrent doxorubicin chemotherapy.