White-Berry Mistletoe (Viscum album L.) as complementary treatment in cancer: Does it help?

Abstract

The word ‘mistletoe’ is generally applied to plants with similar hemiparasitic lifestyles and a certain degree of taxonomical relationship in three families (Loranthaceae, Viscaceae and Eremolepidaceae). The European white-berried mistletoe (Viscum album L.) has attracted special interest in folklore and medicine throughout the centuries. Mistletoe treatment for cancer was introduced in 1920 as part of the anthroposophical medical method. Today, mistletoe extracts are the most frequently prescribed unconventional cancer therapy in central European countries. Mistletoe extracts are complex multi-component mixtures, containing various biologically active substances such as glycoproteins, in particular the mistletoe lectins I, II and III, polypeptides (e.g. viscotoxins), peptides, amino acids, and oligo- and poly-saccharides. Furthermore, they contain innumerable enzymes, sulphurous compounds, fats, flavonoids, phenylpropanes, lignans, alkaloids and various other proteins. Numerous preclinical studies have reported immunostimulatory, cytotoxic and pro-apoptotic effects. In animal models, it can be said that mistletoe extract has direct anti-tumour activity as well as indirect activity through the immune system, and these studies provide a good base for clinical studies.More than 20 prospective clinical trials using mistletoe extracts in patients with various malignancies have been reported. In most of these studies, the authors reported that mistletoe extracts had therapeutic benefit in terms of response rate, overall survival, quality of life and reduced side effects. According to some critical reviews, most studies had at least one major weakness that questioned their reliability. Preparations are usually given as subcutaneous injections, and side effects are generally minimal.