Adjuvant chemotherapy is currently the only treatment proven to be effective for dogs with hemangiosarcoma (HSA), an aggressive and highly metastatic tumor. However, it yields only modest benefits. Targeted immunotherapy is a promising new treatment for human and veterinary cancer patients, and administration of immunotherapy combined with chemotherapy reportedly improves survival time in dogs with HSA. This study assessed the safety and immunologic responses in dogs with HSA to a novel allogeneic tumor vaccine combined with doxorubicin (DOX) chemotherapy. Survival time in a subset of dogs with stage II HSA was also evaluated. Twenty-eight patients received a series of 8 intraperitoneal tumor vaccines over a 22-week period. Chemotherapy protocols were followed concurrently with the vaccines, usually on alternating weeks. The vaccine was found to be well-tolerated by the dogs. The most common adverse effects, diarrhea (18% affected) and anorexia (11% affected), occur at a similar rate in patients receiving DOX alone. A strong humoral immune response was elicited in vaccinated dogs against a novel antigen incorporated into the vaccine, and most dogs were also found to mount an antibody response against canine HSA cells, although the specificity of this immune response was not definitively determined. For the 13 dogs with stage II splenic HSA that were evaluated for disease-free interval and survival time, median survival time was increased over chemotherapy alone (182 days vs. 133 days). There was no significant difference in median disease-free interval for dogs receiving the vaccine and DOX (146 days) versus dogs receiving DOX alone (126 days). Randomized prospective trials are necessary to better compare these survival and disease-free interval results.

COMMENTARY: This study is at the exciting forefront of new and innovative treatment modalities for cancer therapy in companion animals. These therapies are rapidly translating into clinical application. A tumor vaccine has received conditional licensure from the USDA for the treatment of canine oral melanoma, and the allogeneic tumor vaccine described in this study shows sufficient promise for the treatment of canine hemangiosarcoma to warrant further clinical trials.

Evaluation of a novel tumor vaccine in dogs with hemangiosarcoma. U'Ren LW, Biller BJ, Elmslie RE, et al.

J Vet Intern Med 21:113-120, 2007.