EDISCIENCES

ABSTRACT

Introduction Mistletoe (Viscum album extract, VAE) therapy is a valuable part of the integrative oncology toolkit, with several guidelines and systematic reviews supporting its use for improving quality of life and reducing cancer- and treatment-related symptoms, such as fatigue. While there is a substantial body of evidence on subcutaneous (SC) administration, safety data on intravenous (IV) and combined mistletoe administration requires further study. Materials and Methods This analysis based on electronic healthcare record (EHR) and pharmacy data included 23 patients treated with Helixor® mistletoe therapy over the 20-month period between March 2022 and November 2023 in a single UK integrative oncology centre, Synthesis Clinic. Treatment administered included intravenous (Helixor® A and M) and subcutaneous mistletoe therapy (Helixor® A, M and P). Adverse events noted during clinical review around infusions and physician consultations were graded using CTCAE v5. All patients underwent regular haematology and biochemistry monitoring for safety purposes. Results 23 patients, predominantly with metastatic disease (78%), received subcutaneous or combined IV/SC mistletoe therapy alongside a variety of standard of care treatments for a range of solid tumours, including breast, colorectal, ovarian, thyroid, and prostate cancer. No serious adverse events, anaphylaxis episodes or LFT elevations attributable to mistletoe therapy were reported. Mild adverse events included 17% of patients on SC therapy experiencing a grade 1 local injection reaction, e.g. persistent itching, and 33% of patients on IV therapy experiencing short-term grade 1 systemic side effects, e.g. mild flu-like symptoms. No additional treatment for these mild adverse events was required, and no patients discontinued therapy because of adverse events. Conclusions To our knowledge this is the first publication evaluating the safety of intravenous mistletoe administration in the UK. IV and subcutaneous mistletoe therapy was well-tolerated in this group of patients, with minor self-limiting adverse events that did not require specific treatment or cessation of mistletoe therapy.