Mistletoe has been evaluated as a treatment for people with cancer in numerous clinical studies.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
The mistletoe extracts and products studied in clinical trials were Iscador, Eurixor, Helixor, Lektinol, Isorel, abnobaVISCUM, and recombinant lectin ML-1 (refer to the appropriate sections and tables at the end of this section for more information).
The findings from more than 50 clinical trials of mistletoe extracts in patients with cancer have been published, and several systematic reviews and meta-analyses of the results of these studies have been performed. Three of the most recent systematic reviews addressed quality of life (QOL), survival, and symptom relief in patients with various cancer types.[18,20,22] Most studies reported an improvement in QOL.
In one systematic review that examined 26 randomized controlled trials (RCTs), 22 trials reported an improvement in QOL. All 10 of the nonrandomized controlled trials also reported the same benefit. Improvement in fatigue, nausea and vomiting, depression, emotional well-being, and concentration were reported. Some of the studies were well designed, while others reported weaknesses.
Tumor response, QOL, and psychological distress were measured in a review of 21 RCTs of various cancers in which different mistletoe preparations were used either alone, with chemotherapy, or with radiation therapy. Survival times were included in 13 of the studies. Most of the studies reported benefits for patients, although this review was limited by small sample size and methodological weaknesses. Thus, the authors were unable to suggest practice guidelines for the use of mistletoe.
The oldest of these three reviews investigated the results of 10 RCTs that used a variety of mistletoe extracts in patients with various malignancies. There was no difference in survival or other benefits for cancer patients who received mistletoe. Therefore, mistletoe was not recommended as a curative or supportive care therapy.
A systematic review of all controlled clinical studies of mistletoe found consistent improvement in chemotherapy-associated fatigue as well as other QOL measures.