Treatment of tumor-bearing dogs with actinomycin D.

Fifty dogs with advanced malignancies were treated with actinomycin D at doses ranging from 0.5 to 1.1 mg/m2 every 3 weeks. The greatest number of responses was noted in dogs with lymphoma, including dogs that had received prior chemotherapy. Other responding tumor types included anal sac adenocarcinoma, perianal adenocarcinoma, squamous cell carcinoma, thyroid carcinoma, and transitional cell carcinoma. The median time to maximum response for dogs with lymphoma was 7 days, with a median duration of 42 days. Gastrointestinal toxicity was the most frequently observed side effect. A dose of 0.6 to 0.7 mg/m2 appears to be appropriate for treating various malignancies in dogs.