Patient' and social aspects related to complementary mistletoe therapy in patients with breast cancer: A systematic review commissioned by the German agency for Health Technology Assessment.

Purpose: To mitigate side effects of conventional cancer care and improve quality of life, many patients with breast cancer in German-speaking countries opt for mistletoe therapy in addition to standard treatment. To understand the value for users, we evaluated the domain "Patient and Social aspects" in a health technology assessment on complementary mistletoe therapy in patients with breast cancer.

Methods: A systematic review was conducted according to PRISMA guidelines. Fifteen electronic databases and the internet were searched. Qualitative studies were analyzed using qualitative content analysis; quantitative studies were systematically summarized in evidence tables.

Results: Seventeen studies out of 1203 screened publications with 4765 patients and 869 healthcare professionals were included in the review. The median proportion of patients using mistletoe therapy was 26.7% (range: 7.3-46.3%). Predictors for use were younger age and higher educational level. Main reasons for patients' use of mistletoe therapy were to leave nothing untried and to be actively involved in the treatment process. Reasons against use were related to a lack of knowledge or uncertainty regarding effectiveness and safety. Physicians mainly aimed to support the patient's physical condition as main reason for use and a lack of resources and knowledge as main reason against use.

Conclusion: Mistletoe therapy was commonly used in the treatment of breast cancer despite a lack of scientific knowledge among patients and physicians. Transparent communication on motivation for use and its potential effect enables realistic expectations. Relatively small samples of mistletoe therapy users limit the representativeness and validity of our results.