Liposome-Encapsulated Doxorubicin (Doxil) and Doxorubicin in the Treatment of Vaccine-Associated Sarcoma in Cats

Valerie J. Poirier, Douglas H. Thamm, Ilene D. Kurzman, K. Ann Jeglum, Ruthanne Chun, Joyce E. Obradovich, Maura O’Brien, Rogers M. Fred, III, Brenda S. Phillips, and David M. Vail

From the Department of Medical Sciences, University of Wisconsin–Madison, School of Veterinary Medicine, Madison, WI (Poirier, Thamm, Kurzman, Vail); the Veterinary Oncology Services and Research Center, West Chester, PA (Jeglum); the College of Veterinary Medicine, Kansas State University, Manhattan, KS (Chun); the Animal Cancer & Imaging Center, Rochester Hills, MI (Obradovich); the VCA–West Los Angeles Animal Hospital, Los Angeles, CA (O’Brien); the Red Bank Veterinary Hospital and Referral Service, Red Bank, NJ (Fred); and the Pet Emergency and Specialty Center, La Mesa, CA (Phillips). Previously presented at the 20th Annual Conference of the Veterinary Cancer Society, Asilomar, CA, October 2000

The purpose of this randomized, multicenter study was to evaluate the toxicity and efficacy of liposome-encapsulated doxorubicin (LED) and doxorubicin (DOX) in the treatment of feline vaccine-associated sarcoma (VAS). Cats were divided according to their disease status into a microscopic arm (no evidence of gross disease) and a macroscopic arm (evidence of gross disease). Each arm was randomized to receive either LED (1–1.5 mg/kg IV q3 weeks) or DOX (1 mg/kg IV q3 weeks). Thirty-three cats were entered in the macroscopic arm of the study with an overall response rate of 39% (5 complete response and 8 partial response) and a median time to progression of 84 days. Response rates were not different between LED and DOX. Seventy-five cats were entered into the microscopic arm. When compared to a similar historical control population treated with surgery alone, the cats receiving chemotherapy had a prolonged median disease-free interval (388 days versus 93 days). No difference in efficacy was detected between LED and DOX. LED at 1.5 mg/kg induced delayed nephrotoxicosis in 23%, necessitating a decrease in the recommended dosage to 1 mg/kg, and cutaneous toxicosis in 21.7% of treated cats. This study showed that both DOX and LED are efficacious in the treatment of VAS and should be considered in the treatment of this tumor.

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