Background. Traditional mistletoe
therapy in
cancer patients involves subcutaneous applications of Viscum album L. preparations, with doses slowly increasing based on patient responses.
Intravenous infusion of high doses may improve therapeutic outcomes and is becoming more common. Little is known about the safety of this "off-label" application of mistletoe. Methods. An observational study was performed within the Network Oncology. Treatment with intravenous mistletoe applications is described. The frequency of
adverse drug reactions (ADRs) to intravenous mistletoe applications was calculated and compared to ADR data from a study on subcutaneous applications. Results. Of 475
cancer patients who received
intravenous infusions of
Helixor,
Abnoba viscum, or
Iscador mistletoe preparations, 22 patients (4.6%) reported 32 ADRs of mild (59.4%) or moderate severity (40.6%). No serious ADRs occurred. ADRs were more frequently reported to i.v. mistletoe administered alone (4.3%), versus prior to
chemotherapy (1.6%). ADR frequency differed with respect to preparation type, with
Iscador preparations showing a higher relative frequency, compared to
Abnoba viscum and
Helixor. Overall, patients were almost two times less likely to experience an ADR to intravenous compared to subcutaneous application of mistletoe. Conclusion. Intravenous mistletoe
therapy was found to be safe and prospective studies for efficacy are recommended.