Mistletoe extract is derived from the mistletoe plant, a semi-parasitic evergreen. It has a long history of use in traditional medicine and remains a subject of interest in complementary and alternative medicine, particularly for its potential health applications.
Understanding Mistletoe Extract
Mistletoe extract is sourced from different species of the Viscum plant, with European mistletoe (Viscum album L.) being the most commonly studied. The preparation of these extracts often involves fermentation, though unfermented versions also exist. The specific composition of the extract can vary based on factors such as the host tree it grew on, the time of year it was harvested, and the pharmaceutical processing methods used.
The primary active compounds identified in mistletoe extract include mistletoe lectins and viscotoxins. Mistletoe lectins, particularly ML-1 (viscumin), are known for their cytotoxic effects, meaning they can be toxic to cells, and their ability to stimulate the immune system. Viscotoxins are small proteins that also contribute to the extract’s biological properties, including cytotoxic and immune-modulating effects. Beyond these, the extract contains other compounds like phenolic acids, flavonoids, and polysaccharides, which may collectively contribute to its overall effects.
Primary Therapeutic Uses
The most prominent application of mistletoe extract is its use as a complementary therapy for cancer, often alongside conventional treatments like chemotherapy and radiation. Its goals in cancer care focus on enhancing patient well-being.
One primary aim is to improve the quality of life for individuals undergoing cancer treatment. This includes efforts to reduce cancer-related symptoms and alleviate side effects associated with conventional therapies. For instance, studies suggest it may help reduce symptoms and treatment-related toxicities in various cancers, including pancreatic, lung, colorectal, and breast cancers.
Mistletoe extract is typically administered by injection, either subcutaneously (under the skin) or intravenously (into a vein), with subcutaneous injection being the most common route in research. While some preclinical studies indicate that mistletoe extracts may directly influence tumor growth or cause cell death, its primary role in clinical practice is often seen as supportive. It is not considered a standalone cancer cure or an alternative to standard medical care.
Potential Side Effects and Safety
Mistletoe extract therapy is generally well-tolerated, with most side effects being mild and temporary. Common local reactions at the injection site include redness, swelling, itching, and pain. These reactions, often appearing at the beginning of therapy, are sometimes viewed as an indication that the immune system is responding.
Other potential side effects can include mild fever, chills, fatigue, and flu-like symptoms. More serious reactions, such as severe allergic or pseudo-allergic reactions (anaphylaxis), are rare but have been reported. Swelling of the throat, skin, and mucous membranes (angioedema), low blood pressure, and loss of consciousness are also rare but possible severe adverse events.
There are specific contraindications where mistletoe extract should not be used. These include known allergies to mistletoe preparations, acute inflammatory diseases, primary brain tumors, leukemia, malignant lymphoma, and certain autoimmune conditions. Caution is also advised during pregnancy and breastfeeding due to the presence of toxic constituents in the plant. Due to its potency and potential interactions with other medications, particularly immunomodulating drugs, mistletoe extract should only be used under strict medical supervision.
Evidence from Clinical Studies
Clinical research on mistletoe extract, primarily European mistletoe, has largely focused on its use in cancer patients. Studies, including randomized controlled trials, have investigated its impact on quality of life, survival rates, and immune system modulation. Many indicate a positive effect on quality of life for cancer patients, showing improvements in symptom burden and reductions in treatment-related side effects. A systematic review of 26 randomized controlled trials found most reported a benefit in quality of life and reduced side effects.
Regarding survival, the evidence is less conclusive, with some studies suggesting a potential benefit in prolonging survival in certain cancers, such as advanced pancreatic cancer, while others have not found a significant difference compared to control groups. For instance, a study on advanced pancreatic cancer patients showed improved survival with mistletoe extract compared to best supportive care. Mistletoe extract has also been observed to modulate the immune system, leading to increased levels of certain immune cells like T helper lymphocytes, natural killer (NK) cells, and dendritic cells, as well as cytokines such as IFN-gamma and IL-6.
Despite these findings, limitations and challenges exist in the current body of research. These include variations in extract preparations, differences in study designs, and the need for more robust, large-scale clinical trials. The quality of some existing studies has been questioned due to small participant numbers, lack of detailed information, and poor design. More high-quality research is needed to fully establish its role in evidence-based medicine for cancer treatment outcomes.