Comparison of reviews in complementary and alternative medicine (CAM) in oncology: do results depend on methodology?

Objective: The aim of our study was to compare systematic reviews on CAM therapies in oncology in terms of their methodology, results and conclusions. Material: 37 systematic and CAMCancer reviews on CAM in oncology were selected from a systematic search of Medline and the Cochrane library as well as the CAMCancer project. Methods: After an analysis of the literature, we decided to use the AMSTAR instrument in order to assess the reviews. Results: Of the 37 reviews, 18 were on Traditional Chinese Medicine, 8 on non-substance bound methods. Most often used methods in western countries (supplements) are rarely assessed. Most reviews conclude negatively; 12 report positive evidence and 9 ambiguous evidence. Conclusions on acupuncture, Chinese medical herbs and Qigong are contradictory. Cochrane reviews most often point to lack of evidence and conclude positively for only 10% (other systematic reviews 44%; CAMCancer reviews 25%). The quality of systematic reviews is diverse. CAMCancer reviews are not systematic and the description of the studies included is incomplete. Conclusions: For professionals who are looking for easily accessible information on CAM, systematic reviews provide a useful tool. Yet, as the quality of different reviews varies, this quality has to be assessed in order to decide whether to rely on the conclusions drawn. In any case, the entire review should be read, as frequently summary and conclusion are more positive than the evidence found.