Osteosarcoma in Dogs: Immunotherapy Doubles Survival Rates

A study shows that a new immunotherapy protocol can double the survival rate of dogs with osteosarcoma, the most common form of canine bone cancer. Osteosarcoma is a serious form of bone cancer. It is the most common malignant bone tumor in dogs, accounting for about 85% of cases. Certain large dog breeds (German Shepherd, Doberman, Great Dane, Golden Retriever, Saint Bernard, among others) are particularly susceptible to it. Unfortunately, the tumor often results in limb amputation. The recommended treatment for osteosarcoma in dogs is based on surgical removal of the tumor followed by adjuvant cytotoxic chemotherapy. However, in dogs and humans with metastatic tumors, survival is generally short, and life expectancy is only slightly extended, despite the protocols in place. This has prompted veterinarians to seek alternative options and new treatments to improve the animals’ survival. Among the solutions is the activation of the immune system through immunotherapy strategies using therapeutic vaccines, biological vectors, adoptive T-cell transfer, monoclonal antibodies, and modulation of immune signaling. In fact, tumors contain multiple mutations, some of which give rise to neoantigens that make the tumors immunogenic. And even the least immunogenic tumors can trigger detectable immune responses with the help of cancer vaccination and a potent immunological adjuvant. However, this does not necessarily mean that immune responses—even when stimulated—are sufficient to eliminate cancer. However, when T cells are isolated and primed, the situation is quite different. Cytotoxic effector T cells restimulated in vitro with an antigen kill cancer cells in a potent and specific manner. Thus, in rodents, the combination of vaccination against cancer cells—to stimulate the immune response against them—with activated T-cell therapy and the stimulant interleukin-2 completely eliminates spontaneous micrometastases of osteosarcoma. And a new study published in the Journal of Veterinary Internal Medicine shows that the same is true in dogs. A treatment based on ex vivo-activated T cells—generated by an autologous cancer vaccine and stimulated by interleukin-2—increases the animals’ survival compared to amputation alone, doubling survival in some cases. However, while this immunotherapy protocol—which does not involve cytotoxic chemotherapy—appears to be safe, well-tolerated, and effective, increasing overall survival in animals, further studies are still needed to elucidate the underlying immunological mechanisms in order to improve the disease’s response to treatment and overall survival.