Treatment of equine sarcoid with the mistletoe extract ISCADOR® P (viscum album austriacus) – a double-blind placebo controlled study

Equine Sarcoid (ES) is the most common skin tumour in horses with high recurrence rate. No single universal treatment is effective. Viscum album extracts (VAE) are used as adjunct in the treatment of human cancer. We hypothesized that therapy with VAE (Iscador® P) is also effective in Equine Sarcoids. Of 53 horses with ES, 42 were treated solely with VAE or placebo as monotherapy and 11 were treated after selective excision of ES. Horses were randomly assigned to the VAE (n=32) or placebo group (n=21). Horses received increasing concentrations of VAE from 0.1mg/ml to 20mg/ml or physiological NaCl solution 3 times a week over 105 days s.c. Number, localization, size and type of the ES were documented over 12 months. Cure or improvement rate (decrease of tumour size by 50% or more in at least half of the tumours) were assessed after one year. Sarcoid level assessment included analysis of 1 to 7 clinically relevant sarcoids per horse. In the VAE group, 13 horses (41%) showed improvement. Of these, 9 patients showed complete remission (28%). In the control group only 3 cases (14%), all showing complete remission, were classified as improved. In the VAE group 27 ES (38%) showed complete remission and 48 (67%) improvement after one year compared to 9 ES with complete remission (13%; n.s.) and 17 ES (40%; p<0.01) with improvement in the placebo group. VAE (Iscador® P) represent a safe and effective treatment for ES, particularly in cases with multiple sarcoids.