A systematic analysis of the mistletoe prescriptions used in clinical studies

Mistletoe, an anthroposophical medicine, is often recommended as a so-callled alternative medicine (SCAM) for cancer patients. But what type of cancer, what type of mistletoe preparation, what dosage regimen, what form of application?

The aim of this systematic analysis was to assess the concept of mistletoe treatment in published clinical studies with respect to indication, type of mistletoe preparation, treatment schedule, aim of treatment, and assessment of treatment results. The following databases were systematically searched: Medline, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), PsycINFO, CINAHL, and “Science Citation Index Expanded” (Web of Science). The researchers assessed all studies for study types, methods, endpoints and mistletoe preparations including their ways of application, host trees and dosage schedules.

The searches revealed 3296 hits. Of these, 102 publications with a total of 19.441 patients were included. The researchers included several study types investigating the application of mistletoe in different groups of participants: cancer patients with any type of cancer were included as well as studies conducted with healthy volunteers and pediatric patients. The most common types of cancer were:

• breast cancer,
• pancreatic cancer,
• colorectal cancer,
• malignant melanoma.

Randomized controlled studies, cohort studies and case reports make up most of the included studies. A huge variety was observed concerning the type and composition of mistletoe extracts (differing pharmaceutical companies and host trees), ways of applications and dosage schedules. Administration varied widely, e. g. between using mistletoe extract as sole treatment and as concomitant therapy to cancer treatment. The researchers found no relationship between the mistletoe preparation used, host tree, dosage, and cancer type.

A variety of different mistletoe preparations was used to treat cancer patients. Due to the heterogeneity of the mistletoe preparations used, no comparability between different studies or within single studies using different types of mistletoe preparations or host trees is possible. Moreover, no relationship between mistletoe preparation and type of cancer can be observed. This results in a severely limited comparability of studies with regard to the different cancer entities and mistletoe therapy in oncology in general. Analyzing the methods sections of all articles, there are no information on how the selection of the respective mistletoe preparation took place. None of the articles provided any argument which type of preparation (homeopathic, anthroposophic, standardized) or which host tree was chosen due to which selection criteria. Considering preparations from different companies, funding may have been the reason of the selection.

Dosage or dosage regimens varied strongly in the studies. Due to the heterogeneity of dosage and dosage regimens within studies and between studies of the endpoints the comparability of the different studies is severely limited. Duration of mistletoe treatment varied strongly in the studies ranging from a single dose given on one day to the application of mistletoe preparations for several years. Moreover, the duration of treatment frequently varied within the studies. Mistletoe preparations were administered by different ways of application. Most frequently, the patients received mistletoe preparations subcutaneously. The second most common way was intravenous administration of mistletoe preparations. According to the respective manufacturers, this type of application is only recommended for Lektinol^® and Eurixor^®. Other preparations were given as off-label intravenous applications. No dosage recommendations from the respective manufacturers were available. Only in two studies the dose schedules were mentioned: according to the classical phase I 3 + 3 dose escalation schedule or in ratio to the body surface area.

The authors concluded that despite a large number of clinical studies and reports, there is a complete lack of transparently reported, structured procedures considering all fields of mistletoe therapy. This applies to type of mistletoe extract, host tree, preparation, treatment schedules as well as indication with respect of type of cancer and the respective treatment aim. All in all, despite several decades of clinical mistletoe research, no clear concept of usage is discernible and, from an evidence-based point of view, there are serious concerns on the scientific base of this part of anthroposophical treatment.

A long time ago, I worked as a junior doctor in a hospital where we used subcutaneous misteloe injections regularly to treat cancer. I remember being utterly confused: none of my peers was able to explain to me what preparation to use and how to does it. There simply were no rules and the manufacurer’s instructions made little sense. I suspected then that mistletoe therapy was a danerous nonsense. Today, after much research has been published on mistletoe, I do no longer suspect it, I know it.

I would urge every cancer patient to stay well clear of mistletoe and those practitioners who recommend it.