Safety Evaluation and Preliminary Flow Cytometrical Analysis in Dogs With Oral Melanoma Treated with An Immunotherapeutic Dendritic Cell Fusion Vaccine and Concurrent Radiotherapy

Combination of immunotherapy and radiation therapy has been regarded as a new trend in treating cancers. The purpose of this study was to evaluate safety and peripheral blood lymphocyte changes in dogs diagnosed with oral malignant melanoma who received an immunotherapeutic dendritic cell vaccine and concurrent radiotherapy. The vaccine was conducted by fusing allogeneic dendritic cells and autologous tumor cells and was administrated subcutaneously every two weeks. Concurrent hypofractionated radiotherapy was given weekly. Six dogs were enrolled in this pilot clinical study. The treatment was well-tolerated, with only mild radiotherapy-related side effects reported. The median progression-free survival was 146.5 days. Flow cytometrical analysis of the peripheral blood lymphocyte revealed a decreased CD4/CD8 ratio in only one dog, who was also the only long-term survivor. The study provides insights into immune cell changes during immuno-radiotherapy and also supports further expansion of this kind of treatment, investigation of treatment efficacy, and exploration of correlations between immune cell changes and outcome.