Three other therapeutic cancer vaccines are under development for dogs. One is for canine lymphoma, a second for osteosarcoma, and yet another for hemangiosarcoma. All are among the most common types of cancer that befall dogs.
Lymphoma is cancer of the lymph nodes, little “nests” in the lymphatic system. The lymphatic system carries immune cells called lymphocytes throughout the body to fight off disease-causing organisms like viruses and bacteria, which is how the cancer spreads to various tissues in different organs. Lymph fluid carries cancerous cells along with the disease-fighting cells.
Dogs treated with chemotherapy live five to 10 months, on average, but the development of a therapeutic vaccine may increase survival time. Right now, says Tufts veterinary oncologist Kristine Burgess, DVM, researchers have “just completed a phase one trial to show the vaccine is well tolerated, with few to no side effects. In addition, a few dogs entered into the research did extremely well.” Their cancer didn’t spread.
The vaccine to fight osteosarcoma, or bone cancer, has also undergone a phase 1 trial, and the dogs in that research came through without side effects, too. The investigators, working out of the veterinary school at the University of Pennsylvania, will probably move soon to a gold standard placebo-controlled trial in which dogs with osteosarcoma are assigned to the actual vaccine or a placebo. The scientists are hopeful because preliminarily, a few of the dogs did exceedingly well.
Even if the vaccine turns out to work in a larger study, dogs with osteosarcoma will still need to undergo amputation of the limb with the bone cancer as well as chemotherapy. But they should enjoy a much longer survival time. Stay tuned.
Research is also beginning on a therapeutic vaccine against hemangiosarcoma, cancer of the cells that form blood vessels. Survival time after removal of the tumor is limited to about three or four months, in large part because the spread of hemangiosarcoma from the blood vessels to other tissues is virtually 100 percent. But if a vaccine proves helpful, survival time will of course increase.
The most common location for the start of hemangiosarcoma is the spleen. If researchers can create a safe, effective vaccine by using the cells of splenic tumors removed surgically (they are in the very early stages of their work here), it will have the potential to radically change the course of the disease.
Incidentally, research is going on at the Dana Farber Cancer Institute in Boston to develop a therapeutic vaccine to combat melanoma in people. “It’s on the boards,” Dr. Burgess reports, “but it’s still in development. They’re testing for safety right now.”
The vaccine for humans is actually made from proteins found on melanoma tumors. Researchers kill the cells of the tumor itself, but certain proteins remain. Scientists are combining those proteins with chemicals that will activate the immune system, with the aim of giving the combination to the cancer patient in vaccine form. The goal is for the body to say, “Whoa, I know those proteins. I’ve seen them in my body. I need to destroy them.”
