Feline vaccine-associated sarcomas are locally invasive and have a high rate of metastasis. Doxorubicin is efficacious against soft tissue sarcomas in cats; however, myelosuppression and the potential for cumulative nephrotoxicosis have been reported with its use. This study of 108 cats with microscopic and macroscopic disease evaluated the efficacy and toxicity of liposome-encapsulated doxorubicin (LED) and doxorubicin. After surgical removal of tumors, the cats were assigned to receive either LED (1 to 1.5 mg/kg IV) or doxorubicin (1 mg/kg IV). Cats with microscopic disease received five treatments 3 weeks apart; those with macroscopic disease received treatment every 3 weeks either until progressive disease was noted or five treatments were given. Response rates did not differ between the doxorubicin and LED groups. Cats with microscopic disease had considerably better response than historical controls treated only with surgery (388 days vs. 93 days). The response in cats with macroscopic disease was short (median, 84 days).

Some cats in both groups had mild, self-limiting gastrointestinal signs. When eight cats receiving 1.5 mg/kg LED experienced azotemia, the dose was reduced to 1 mg/kg. Only one cat on the lower dose experienced azotemia. Five cats receiving doxorubicin experienced azotemia. Five of the cats treated with LED had cutaneous signs-alopecia, hyperpigmentation, erythema, and papule formation-of varying degrees. Four cats in the LED group experienced an acute anaphylactic reaction during the first infusion. They responded to treatment, and drug delivery was reinitiated.

COMMENTARY: A prospective, randomized clinical trial would be needed to prove the benefit suggested in these studies. Further studies evaluating multimodality therapies are necessary. A combination of chemotherapy, surgery, and radiation therapy may be the most efficacious regimen for treating vaccine-associated sarcomas in cats. This study was supported in part by a grant from the Vaccine-Associated Feline Sarcoma Task Force and ALZA Pharmaceuticals, Inc.

Liposome-encapsulated doxorubicin (Doxil) and doxorubicin in the treatment of vaccine-associated sarcoma in cats. Poirier VJ, Thamm DH, Kurzman ID, et al. J Vet Intern Med 16:726-731, 2002.