Clinical Studies

Novel treatment for vaccine-associated sarcomas in cats

“Feasibility and tolerability of Yttrium-90 radiogel brachytherapy for the treatment of feline vaccine-associated sarcomas”


Purpose of Study

Vaccine-associated sarcomas (VAS) are aggressive tumors that can arise in some cats in the spot where they receive vaccinations. The best treatment for VAS is a combination of aggressive surgery, where the surgeon removes the tumor along with a large amount of surrounding tissue in order to ensure complete removal, and follow-up radiation treatment. Unfortunately, because many of these sarcomas occur in areas of a cat’s body where a surgeon cannot take much surrounding tissue, the tumors often return. The purpose of this study is to see if a novel form of radiation therapy, Yttrium-90 RadioGel, can be successfully used in cats to shrink vaccine-associated sarcomas, making them more easily removed by surgery.  Yttrium-90 RadioGel is a type of brachytherapy. Brachytherapy is a procedure that involves placing radioactive material directly into the tumor and allows doctors to give higher doses of radiation to more specific areas of the body, in a shorter amount of time with fewer side effects.


This pilot study may lay the groundwork for a clinical trial using Yttrium-90 RadioGel to treat cats with vaccine-associated sarcomas.  If Yttrium-90 RadioGel proves to be effective at reducing tumor size so that surgeons can completely remove the tumor, it could change both the way vaccine-associated sarcomas are treated and extend the life expectancies of cats who get VAS. This study will cover the cost for three of the four required CT scans, the Yttrium-90 RadioGel and its administration, and surgery costs up to $3,000.

Enrollment Requirements

Enrolled cats must have a previously diagnosed vaccine-associated sarcoma, fibrosarcoma or other soft tissue sarcoma suspected to be vaccine-associated in origin. Cats must be healthy enough to go about their daily routine and need to have a life expectancy of at least 12 weeks. They cannot have had previous radiation therapy for the sarcoma.

Treatment Methods

Once your cat has a confirmed diagnosis of vaccine-associated sarcoma and has been admitted into the study, you will schedule an injection date with the oncology service. On the injection date, your cat will be anesthetized and the tumor site will be shaved before the RadioGel is injected into the tumor. Enrolled cats will need to stay in the isolation ward at the Veterinary Teaching Hospital for at least one night for observation. Three weeks after RadioGel injection, enrolled cats will need to return to WSU for a CT scan to evaluate the size of the tumor. Six weeks after RadioGel injection, enrolled cats will return to WSU for an exam, a CT and then will have surgery to remove the tumor. Following surgery, cats will need to stay at WSU until they are deemed healthy enough to return home by the surgeon (approximately 3-5 days). Over the next two years, participating cats will return to WSU for 7 recheck appointments.

Owner Responsibilities

Owners are responsible for the costs associated with their cat’s tumor diagnosis (blood work, chest radiographs, cytology, exam fee, CT) and for surgery costs incurred beyond $3,000. They will be required to bring their cat to WSU-VTH for staging, the Yttrium-90 RadioGel injection day, a 3-week tumor evaluation CT, on surgery day and for seven follow-up appointments over the next two years.

Contact Information

For more information please contact:

Valorie Wiss, Clinical Studies Coordinator
Office: 509-335-0798
Cell: 509-432-5345

Dr. Megan Duffy
Clinic: 509-335-0711