Radioactive Beads Latest Weapon In Fighting Cancer In Dogs, Cats

When surgery can't be performed or isn't enough to remove cancerous tumors, veterinarians at Kansas State University's College of Veterinary Medicine are using a new, implantable radiation treatment option. According to Dr. Ruthanne Chun, assistant professor of clinical sciences at K-State, brachytherapy is for dogs or cats that have certain tumors that aren't likely to spread to other parts of their body.

"Brachytherapy is something we've tried do more and more of here," Chun said. "There are maybe two or three other veterinary colleges that do it, so we are really riding the edge of that wave in being able to offer this service."

After as much of the tumor as possible is removed, a hollow, sterile plastic tube called an "after-loading tube" is sutured into the tumor bed. After the wound is closed, Chun said the radioactive beads are "essentially strung together on a plastic wire" and "fed" into the after-loading tubes. Once clamped in place, they begin to emit a set amount of radiation into the tumor bed.

"We know from past experience how much of a dose, how much radiation, a tumor needs to be effectively treated," Chun said. "We can calculate roughly how much radiation per day the tumor bed is receiving. After it has gotten its set dose, we sedate the animals, remove the tubes and the beads and they're done with their therapy."

Because the beads provide a continuous, low level dose of radiation, animals must be kept in isolation. Chun said owners are not allowed to visit their pets while they are receiving brachytherapy. The pets may still be allowed to go outside but must be kept away from other animals. They must also be handled only by veterinarians licensed to work with radioactive substances.

Chun said the treatment is, in some ways "much nicer" than conventional forms of radiation therapy. Animals do not have to go under anesthesia multiple times and the duration of the therapy is much shorter than with conventional or external beam radiation therapy.

"For conventional radiation therapy where you use an external beam unit, the animal has to lie still for the radiation therapy; this requires daily anesthesia anywhere from 10 to 15, or 20 times -- depending on what type of tumor it is," Chun said. "And the costs really add up when you have to anesthetize the animal each time and allow time for recovery. It's much harder on the animal than doing the implant therapy."

Chun said not all tumors can receive the implant, but that it is a good treatment option for a lot of different tumors.

"It seems to be as successful as more conventional forms of therapy," Chun said. "But we need two or three years from now before we can say our dogs have survived as long as, if not longer than, dogs treated with other forms of radiation."