Ifosfamide in Cats
August 1, 2002 (published)
Susan Little DVM, DABVP (Feline)

Winn Feline Foundation Progress Report
By Susan Little DVM, Diplomate ABVP (Feline)

August 2002

Evaluation of Ifosfamide in Cats with Soft Tissue Sarcomas
Investigators: K.M. Rassnick and others
College of Veterinary Medicine
Cornell University, Ithaca, NY

Funded 2000, 2001

Sarcomas are one of the most common feline cancers and also one of the most difficult to treat. They are malignant cancers of connective tissues and may form under the skin or attached to deeper structures. Since 1991, the rate of fibrosarcomas in cats has increased in association with some vaccines (especially rabies and feline leukemia). It is extremely difficult to remove these tumors completely with surgery and many chemotherapy drugs are ineffective. Even with radiation, the cure rate is very low.

In human medicine, a chemotherapy drug called ifosfamide is one of the few drugs that have proven effective against sarcomas. In the first part of their research, Dr. Kenneth Rassnick and his colleagues at Cornell University evaluated the effects of varying doses of ifosfamide in ten cats with various types of sarcomas. The drug must be given intravenously in conjunction with intravenous fluid therapy for several hours. A drug called mesna is administered at the same time in order to protect the lining of the bladder from any potential toxic effects as the ifosfamide is eliminated in the cat's urine. However, it is only necessary to administer ifosfamide once.

Twenty-nine cats were monitored carefully for any adverse effects of various doses of the drug and for their response to treatment. No significant adverse effects on any body system were found with the protocol used by the researchers. Two cats in this part of the study achieved remissions of their sarcomas.

Dr. Rassnick and his colleagues will continue to evaluate the effectiveness of ifosfamide to induce remissions in cats with sarcomas, and determine if multiple treatments are safe. The results of their work could provide an effective therapy against vaccine-associated fibrosarcomas and other types of sarcomas, and has the potential to save many feline lives in the future.

For further reading:

Rassnick, K., R. Page, et al. (2003). Clinical evaluation of ifosfamide for treatment of feline vaccine-associated sarcomas. Proc 21st Amer Coll Vet Intern Med Forum, Charlotte, NC.