Liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE): a randomized clinical trial in dogs with mammary carcinoma.

In this prospective randomized double-blind clinical study the anti-tumour activity of liposome-encapsulated muramyl tripeptide phosphatidylethanolamine (L-MTP-PE) was evaluated as an adjuvant immunotherapy in dogs with mammary tumours of the simple carcinoma type. Dogs were randomized after surgery to one of two treatment groups, in which they were treated with either L-MTP-PE (2 mg/m2 i.v.; Ciba Geigy Basel, Switzerland) twice weekly for eight weeks, or with empty liposomes according to the same protocol. The minimal follow-up period was one year. Thirteen dogs were entered in the L-MTP-PE group and fourteen dogs in the placebo control group. Only minor toxicities (fever and shivering during 10-24 hours) were seen in six dogs treated with L-MTP-PE, these being mainly of the smaller breeds. At the time of evaluation seven dogs were still disease free. In the other twenty dogs the disease-free period (DFP) was ended by local recurrences in 16 and by distant metastases in 4. The difference in DFP between dogs treated with L-MTP-PE (median 165 days, range 15-905) and dogs in the placebo group (median 133 days, range 27-659) was not significant. The difference in overall survival between the dogs treated with L-MTP-PE (median 222 days, range 36-905) and those receiving the placebo (median 182 days, range 54-659) was also not significant. It was concluded that liposome-encapsulated MTP-PE was not efficacious in the treatment of dogs with mammary carcinoma.