Mistletoe is often used as complementary therapy in oncology. The anti-tumor effects of mistletoe (Iscador®) are well documented in-vitro in respect to inhibition of cell proliferation, induction of apoptosis, segmental activation of immune competent cells and trapping of chemotherapeutic drugs within cancer cells by modulating the inhibitory potential of P-glycoprotein (P-gp)-mediated transport of cell toxifying substances (cytotoxic drugs). However, the clinical activity of mistletoe treatment remains still controversial. Implementation of mistletoe therapy as supportive care into anti-cancer programs should be based on the best evidence and must continually be evaluated to ensure safety, efficacy, collection of new data, and cost-effectiveness. Useful domains that can be evaluated include symptom control, adherence to conventional treatment protocols, quality of life, individual outcome and potential advantages of a whole-system health approach. Here we report the results of a multicenter, controlled, retrospective and observational pharmacoepidemiological study in patients suffering from a pancreatic carcinoma. After surgery the patients were treated by adjuvant chemotherapy with gemcitabine supported by Iscador®, or with gemcitabine alone, or any other best of care, but not including Iscador®. Using a novel methodological pharmaco-epidemiological design and statistical approach it could be shown that Iscador® offers benefits - symptom control, overall survival - as supportive care within gemcitabine protocols of patients with surgically resected pancreatic carcinoma.