Use and Safety of Viscum album L Applications in Cancer Patients With Preexisting Autoimmune Diseases: Findings From the Network Oncology Study

Background: Viscum album L (VA, mistletoe) extracts are commonly used in integrative oncology. Here the clinical safety profile of additional VA-treatments to standard care in cancer patients with preexisting autoimmune diseases was analyzed. Methods: In this observational cohort study medical data and recorded adverse events (AEs) of treated patients were retrieved from the Network Oncology registry and a safety analysis was performed. Results: A total of 106 patients (median age 63 years) treated with add-on VA-extracts were analyzed. Most frequent autoimmune diseases were Hashimoto’s thyroiditis (27%), psoriasis (19%), and ulcerative colitis (15%). Seventeen patients (16%) experienced VA-related AEs, but neither long-term side effects nor VA-therapy discontinuations were recorded. In a subgroup of 30 patients receiving long-term VA-therapy no exacerbations or flares of underlying autoimmune diseases were recorded. Additionally, a significant halving of overall AE-rates was observed during VA-treatment periods (p= 0.019). Conclusions: Our findings suggest that add-on VA-therapy in cancer patients with preexisting autoimmune diseases as Hashimoto’s thyroiditis, psoriasis, ulcerative colitis, Grave’s disease, and some rheumatic diseases is safe. No higher rates of VA-associated AEs were observed and the overall AE-rates were significantly lowered in VA-therapy periods. However, results should be interpreted with caution in light of the study’s observational character.