Background: Anthroposophic Mistletoe therapy is a widely used complementary cancer treatment.
Objective: To evaluate prospective clinical trials on the effectiveness of anthroposophic mistletoe therapy for cancer.
Design: Systematic review.
Material and methods: Search of 9 electronic databases, reference lists and extensive expert consultations. Criteria-based assessment of methodological study quality.
Results: 16 randomized (RCT) and 9 non-randomized (N-RCT) controlled trials were identified that investigated mistletoe treatment of malignant diseases. Statistically significant benefit for survival was reported in 8 of 17 trials (in 5 of 10 RCTs), for disease-free survival and tumour recurrence in none of 2 RCTs, for remission of tumour and malignant effusion in 1 RCT and 1 N-RCT of 4 controlled trials, for quality of life (QoL) in 3 of 5 RCTs, and for QoL and reduction of side effects of cytoreductive therapies (chemotherapy, radiation or surgery) in 5 of 7 trials (3 of 5 RCTs). Methodological quality of the controlled trials differed substantially; some had major limitations while others were reasonably well conducted. 12 single-arm cohort studies were identified. 5 of 7 studies found substantial tumour remission in various cancers, one study reported remission of CIN, and 4 studies remission of malignant pleural effusion or ascites. Quality of reporting in cohort studies was mostly reasonably good. Mistletoe application was well tolerated.
Conclusions: Regarding quality of studies and consistency of results, the best evidence for efficacy of mistletoe therapy exists for improvement of QoL and reduction of side effects of cytotoxic therapies (chemotherapy, radiation). Survival benefit has been shown but not beyond critique. Tumour remissions are described in cohort studies that investigate the application of high dose or local mistletoe extracts. As several reasonably well-conducted studies indicate beneficial effects, further properly designed trials should be encouraged to investigate clinical efficacy and its possible dependency on the mode of application.