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] Reviewed in [15,16,17,18,19,20] One phase II study in Israel involved carboplatin /gemcitabine in combination with mistletoe as a complementary treatment in patients with non-small cell lung cancer (NCT00516022). Most studies have been conducted in Europe, primarily in Germany and Austria. However, in 2002, the National Center for Complementary and Alternative Medicine in cooperation with the National Cancer Institute (NCI) began accruing patients to a phase I trial (NCCAM-02-AT-260) of mistletoe (Helixor A) and gemcitabine in patients with advanced solid tumors. The Helixor A and gemcitabine combination showed limited toxicity with clinical benefit in 48% of patients. The trial is now closed and the data is being analyzed. Another U.S. trial (NCT00283478) of the mistletoe extract Iscar with gemcitabine versus gemcitabine alone as a second-line therapy for non-small cell lung cancer patients who have failed one prior line of chemotherapy has been completed.
The mistletoe extracts and products studied in clinical trials were Iscador, Eurixor, Helixor, Lektinol, Isorel, Abnoba-viscum, and recombinant lectin ML-1 (refer to the tables at the end of this section for more information).
Approximately half of the reported studies were controlled studies, and a majority of these were randomized clinical trials. Survival was the principal endpoint measured in most reported studies; however, other endpoints included tumor response, tumor recurrence, and quality of life. A systematic review of all controlled clinical studies of mistletoe found consistent improvement in chemotherapy-associated fatigue as well as other quality-of-life measures.
Although mistletoe was found to be therapeutically effective in most of the reported studies, many of the studies had one or more major weaknesses that raised doubts about the reliability of the findings. These weaknesses include registration of small numbers of patients; presence of large numbers of patients who either were not evaluable or were otherwise excluded from the analyses; failure to adequately document mistletoe use, mistletoe dose, and/or interruptions of mistletoe use; absence of control subjects or use of historical control subjects; use of inadequate randomization procedures; absence of treatment blinding; extensive use of subset analysis; and the measurement of mean as opposed to median survival. (Note: In studies with small numbers of patients, the mean survival time [i.e., the average survival time] can be greatly exaggerated if one or more patients exhibit unusually long survival; median survival, therefore, is a less biased measure.) In addition, evaluation of the studies is often hindered by incomplete descriptions of the study design and by incomplete reporting of clinical data, including data about previous and concurrent therapies received by the patients. A selection of studies is discussed below, organized by the type of mistletoe extract used.