Veterinarians at The Animal Medical Center (AMC) and researchers at Memorial Sloan-Kettering Cancer Center (MSKCC) have collaborated to study the efficacy of a vaccine against canine malignant melanoma (CMM). Because this deadly cancer is virtually resistant to chemotherapy and radiation in its late stages, new approaches are being investigated, including vaccines that harness the immune system.

Canine malignant melanoma is the most common oral cancer in dogs and accounts for one out of twenty cancer diagnoses. It is highly aggressive, occurring spontaneously in the mouth, nail bed, and foot pad. CMM is most successfully treated in its early stage by surgery. However, the prognosis is not good if there is a late diagnosis or the cancer has spread to another organ. In advanced stages, the median survival is 2 to 3 months.

In this study, nine dogs that naturally developed canine malignant melanoma were treated with a new DNA-based vaccine. The treatment more than tripled their median survival from an expected 90 days to an average of 389 days. Two showed no evidence of disease when they were checked after completion of the vaccine regimen. Four dogs survived for over 400 days with the longest survivor still alive after more than 615 days.

The results of the study are reported in the April issue of Clinical Cancer Research. The vaccine continues to be studied at AMC. A parallel clinical trial began last fall at MSKCC for people with high risk of melanoma recurrence.