An hGM-CSF DNA-Cationic Lipid Complexed Autologous Tumor Cell Vaccine did not Improve Remission Duration in Dogs with Lymphoma

Introduction: Lymphoma is one of the most common cancers in dogs and while clinical remission can be induced using chemotherapy, very few dogs are cured. Since cytokine‐adjuvanted autologous whole‐tumor‐cell vaccines (ATCV) can induce potent antitumor immune responses against otherwise non‐immunogenic cancers we initiated a study of such an approach in dogs with lymphoma. Methods: Following achievement of a complete remission using a 19‐week CHOP‐based chemotherapy protocol, 51 dogs with B‐cell lymphoma were randomized to receive 8 treatments (4 weekly, then 4 additional at q2wk intervals) of vaccine or lipid‐equivalent placebo. Dogs were followed monthly for assessment of remission duration and survival. Surrogate indices of immune response (delayed‐type hypersensitivity, interferon‐γ quantitative RT‐PCR, lymphocyte proliferation, and flow cytometry for lymphoma‐specific antibodies) were also investigated before and after vaccination. Results: No significant difference in median remission duration was observed between dogs receiving vaccine (277 days) or placebo (258 days); the Kaplan‐Meier curves were virtually super‐imposable. No significant differences in surrogate indices of immune response were noted pre‐ and post‐vaccination. Conclusions: In this context, an hGM‐CSF DNA‐cationic lipid complexed ATCV vaccine did not enhance remission duration in dogs with lymphoma, likely due to lack of vaccine‐induced tumor‐specific immunity.