Dr. Chelsea Tripp treats recurring tumors with electrochemotherapy.
When Dr. Katja Zellmer, large animal surgeon in the OSU Veterinary Teaching Hospital (VTH), read about electrochemotherapy in her journal club, she realized it might be a good treatment option for a client whose horse had a sarcoid that was unusually aggressive.
Dr. Zellmer had resected most of the horse’s tumor surgically, and had injected chemotherapy into the wound bed and surrounding tissue. “Things seemed to respond well,” she says, “but about two weeks ago, the owner noticed a new sarcoid that was rapidly growing adjacent to the area that had been looking better.”
So Dr. Zellmer contacted Dr. Chelsea Tripp, head of Veterinary Cancer Specialty Care in Lynwood, Washington, who is experienced in the use of electrochemotherapy, and arranged for her to come to Corvallis to treat the horse.
When Dr. Shay Bracha, veterinary oncologist at the VTH, heard about Dr. Tripp’s pending visit, he arranged for one of his patients, a thirteen-year-old golden retriever named Nikko, to receive treatment on the same day. Nikko has had several soft tissue sarcomas removed surgically, and has received traditional chemotherapy, but his tumors keep returning.
Electrochemotherapy has been used in human medicine for several years. In some cases, it can triple the efficacy of cancer drugs. It works because, when a cancer cell is exposed to a strong electric field, the cell’s membrane becomes more permeable. Dr. Tripp injects a cancer drug like Cisplatin directly into the tumor and then uses a probe to deliver multiple electric pulses around the surface area of the tumor. “It basically drives the chemo drug into the tumor and traps it there,” says Dr. Tripp. The duration of each pulse is only one-hundred microseconds, so she treated the two tumors on Nikko’s leg in just a few minutes. Although there is some mild discomfort during treatment, there are limited side effects from the chemotherapy.
Dr. Tripp has found tumors of this kind to be responsive to electrochemotherapy in approximately ninety percent of cases. “Sometimes a repetition of the treatment is needed,” she says. Dr. Tripp hopes to see Nikko’s tumors begin to shrink in a few weeks.
Although this treatment has primarily been used on external tumors, new electrochemotherapy techniques have been developed for treatment of internal tumors using surgical procedures like endoscopy. “Intraoperative use of electrochemotherapy can be beneficial in cases like bladder tumors where it is very difficult to get all the tumor,” says Dr. Tripp. “I just have to be able to get to it.”
Dr. Bracha is working with Dr. Tripp to provide electrochemotherapy to more VTH patients by scheduling semi-regular treatment days in which she can see many patients on a one-day visit.