Feline injection site sarcoma (FISS) is an aggressive form of cancer in cats associated with the administration of vaccines and injectable medications, affecting about one in 1,000 vaccinated cats. This cancer was once thought to be a rare side-effect of rabies vaccines, but experts now believe it can occur following any kind of injection —even microchipping.
Elizabeth Maxwell, DVM — who has recently completed a residency in small animal surgery at the University of Illinois Veterinary Teaching Hospital in Urbana — has been investigating a treatment option for FISS over the past three years. “The current theory is that when a cat is given a shot, a chronic inflammatory reaction develops at the site of the injection, triggering abnormal transformation of cells,” explained Dr. Maxwell.
“We know that FISS is treatable with surgical removal of the tumor, radiation therapy and chemotherapy, but these approaches can be very aggressive, expensive for clients, and risky for old or very sick cats,” said Dr. Maxwell. “The best prognosis lies in surgery that often requires amputation or removal of part of bones or parts of the abdominal wall. Even then, it’s always possible that the cancer can come back if a part of the tumor escaped notice or spread.”
Working with Heidi Phillips, VMD — associate professor of small animal surgery — Dr. Maxwell is investigating a cost-effective, local treatment option for cats with FISS. Their research focuses on the chemotherapeutic drug called carboplatin — which is used commonly in both dogs and cats to treat cancer — but can be associated with kidney failure or gastrointestinal problems when injected into the bloodstream. Dr. Maxwell feels that if carboplatin could be administered to the tumor without reaching other parts of the body, it might prove to be safer and a less expensive treatment approach than the current standard of care for FISS.
Maxwell and Phillips are studying whether a tiny clay-like bead containing carboplatin can be placed under the patient’s skin, where the bead would dissolve and diffuse the drug into the tissues. “Our hope is that by using the beads, the drug will affect only the tumor and the tissue around it and won’t spread and damage the rest of the body. This procedure would also be minimally invasive and allow an affordable treatment option to use alone or in conjunction with surgery. — Catnip staff