Mistletoe Therapy for Breast Cancer

Mistletoe is one of the most widely studied alternative therapies for cancer. But is it effective? Is mistletoe therapy good for breast cancer, specifically?

About the Plant

Mistletoe is a parasitic plant that attaches itself to the branches of other shrubs and trees that grow near it, and it burrows into the inner wood of the host and sucks the water and nutrients from the sap of that host plant. Kind of disgusting, right? So how could such a plant be of benefit for breast cancer? Read on, and I’ll explain.

There are over 1300 species of mistletoe plants growing across the world including Europe, North America, Africa, Asia, Australia and New Zealand. However, the focus of this article is mainly on European Mistletoe (Viscum album), the most studied species.

Mistletoe has been utilized as a powerful herbal medicine for hundreds of years for many different ailments. More recently, Rudolf Steiner (1861-1925), the Austrian philosopher and founder of anthroposophical medicine, introduced it as a powerful anticancer medicine.

How Mistletoe is Being Utilized in Cancer Clinics

Mistletoe therapy is prescribed by naturopaths and integrative doctors to help stimulate the immune system, improve quality of life and improve symptoms for those going through conventional therapies like chemotherapy and radiotherapy, for reducing tumor size and slowing the progression of the disease.

Mistletoe is most commonly given as a subcutaneous, intramuscular injection, or as an intravenous infusion given over a period of hours. Mistletoe can also be taken as a capsule in a supplement or taken as a tea/tincture (but the latter are considered to be much less effective).

Mistletoe Product Names

Mistletoe products are marketed under the names of Iscador®, Helixor®, Eurixor®, Lektinol®, Isorel® and abnobaVISCUM®. Generally, these are made as extracts and prepared in water and alcohol-based solutions or as a water-based solution. The best ones are standardized to the lectin content, and I’ll explain more about that below.

Mistletoe’s Phytochemicals

Mistletoe contains a number of biologically active compounds including lectins (classified as I, II and III), viscotoxin (a protein), flavonoids, amino acids, triterpenes, phenylpropanoids, phytosterols, alkaloids, polyalcohols, polysaccharides, glycosides and tannins.

Of those phytochemicals, it is mainly the lectins, and in particular lectin I, that have been the most studied. [1]  As noted above, most commercial products are standardized to the lectin content, which means that the product contains a specific amount of lectins, guaranteeing that the consumer is buying a product in which the chemistry is consistent from bottle to bottle. However, I suspect it is all of the compounds listed above working in synergy that gives mistletoe its therapeutic potential.

Research Studies on Mistletoe

Quite a number of studies have been conducted over the past several decades to assess whether mistletoe is effective as a treatment for cancer. The website pubmed.gov has over 800 studies on mistletoe. Overall, the news is good – mistletoe therapy appears to be particularly effective for improving the immune system and quality of life in cancer patients.

Having said that, the studies vary quite a bit in quality, which is usually the case with natural products, ranging from case reports on a single individual to randomized controlled trials. There have also been quite a few systematic reviews and meta-analyses of research, always helpful when deciding whether a substance has benefit. I’ve done my best to summarize the studies I found to be most helpful.

Research: Immune System Benefits of Mistletoe

Mistletoe lectins and polysaccharides have been shown in research to have immune boosting properties, to increase the cytotoxic (cancer cell killing) activity of white blood cells known as macrophages, to stimulate phagocytosis (cancer cell eating) by immune cells, to increase the secretion of cytokines known as TNF-alpha, interleukin-1, interleukin-2 and interleukin-6, to activate T-cells, and to increase the number and activity of natural killer (NK) cells, improving their ability to interact with and more effectively recognize cancer cells [2]–[9].

One German clinical study in particular [10] investigating the effects of mistletoe for breast cancer patients found that it gave “statistically significant increases of defined peripheral blood lymphocyte subsets (helper T-cells, natural killer (NK)-cells)”, enhanced interleukin-2 receptors and had other immune-related benefits.

One small Swiss study [11] found that mistletoe therapy given over a longer term (2 or more years) may have a greater benefit for the immune system than shorter term therapy. Although a small study, the data indicated that half of the patients (6 out of 12) with long-term mistletoe treatment had a continuous complete remission, whereas only two out of 15  patients with short-term treatments had complete remission.

A small Korean clinical trial [12] investigated mistletoe therapy in 20 women with early stage  breast cancer who had surgery, followed by chemotherapy and radiation. The researchers found that subcutaneous injections of mistletoe for 7 weeks immediately following surgery resulted in significant increases in the concentration of Interleukin-6 (an important cytokine, or chemical messenger, involved in immune response) and Interferon-gamma (the primary activator of macrophages, natural killer cells and neutrophils), all of which you want working on your behalf for killing cancer cells!

Research: Anti-Tumor Properties of Mistletoe

It is believed that the lectins, as well as the viscotoxins and alkaloids in mistletoe all play a part in the cytotoxic activity of mistletoe. A number of cancer pathways appear to be involved, including inhibition of protein synthesis, promotion of apoptosis (planned cell death) and necrosis (cell death). 

Studies that investigated tumor response, including incidence of recurrence and remission, are somewhat inconclusive. A Cochrane review [13] included 21 randomized controlled trials, seven of which investigated tumor response. Of those seven studies, only two reported a possible benefit in tumor response, while the other five reported no benefit. 

In 2008, a 37-year-old American woman, Ivelisse Page, was diagnosed with stage IV colon cancer. Despite having 15 inches of her colon resected and losing 28 lymph nodes, the cancer migrated into her liver. She had a second surgery in which 20 percent of her liver was removed. One of Page’s doctors, Peter Hinderberger, MD, suggested she try mistletoe – he’d seen patients do well after mistletoe injections. Her oncologist, Dr Luis Diaz at the Johns Hopkins Kimmel Cancer Center, had a look at the studies on mistletoe and decided to see how Page went with it. Dr Diaz stated, “… as soon as she went on it, she started feeling better. That’s a universal feature I’ve seen in all patients who get mistletoe.” Page is now cancer-free and in an effort to get mistletoe therapy to be more widely utilized for American patients, she and her husband formed a nonprofit called Believe Big, to raise funds for a clinical trial in the United States. This research is ongoing but has been curtailed due to the coronavirus pandemic, along with another, similar trial ongoing in the United Kingdom. (For more information, to read her story, or to donate, paste this link into your browser: https://believebig.org/clinicaltrial/ )

A 2009 systematic review [14] investigating breast and gynecological cancers included nine studies that were assessed for tumor remission or time to relapse after mistletoe treatment. Of these nine studies, three reported a significant benefit from mistletoe therapy.

A 2014 German paper [15] discussed a case report of a 78-year-old patient with adenoma of the colon. This patient had a relapse of cancer that had been treated 5 years previously with surgery only. He had refused chemotherapy and the recurrent cancer wasn’t a good candidate for surgery again. He was treated with two injections of mistletoe directly into the tumor site to limit tumor growth. 8 months later, the man was cancer free.

A 2016 cell study [16] investigated the possible interaction between mistletoe and the monoclonal antibody drug Trastuzumab (Herceptin) for those with HER2+ breast cancer. Researchers found that mistletoe did not interfere with the cytotoxic activity of the drug, and that the two in combination seemed to exhibit complementary anti-cancer effects, at least in the test tube.

Research: Quality of Life Improvement for Cancer Patients

Mistletoe therapy is widely known for its benefits in improving the quality of life and management of symptoms for cancer patients. We’ve already seen the benefits for the immune system – most studies demonstrated that mistletoe is effective for stimulating immune function, which is quite important for the well-being of these patients. In addition, mistletoe therapy can help with a number of other factors.

Some of the documented improvements in quality of life can be attributable to how mistletoe helps with symptom management, especially in relation to chemotherapy. [17]-[18] Interestingly, doctors using a combination of mistletoe with chemotherapy and/or radiotherapy for their cancer patients will tell you that the mistletoe seems to improve the side effects of chemotherapy and radiotherapy including nausea and vomiting, fatigue and diarrhea, and improves recovery from those side effects. 

A 2008 Cochrane review [13] of mistletoe studies noted that most of the studies were not of high methodological quality, but that “there is some evidence that mistletoe extracts may offer benefits on measures of QOL [quality of life] during chemotherapy for breast cancer.

A small 2013 randomized controlled trial [19] with 123 breast cancer patients also receiving adjuvant chemotherapy showed an improvement in quality of life (eg less insomnia, loss of appetite, diarrhea, nausea and vomiting, constipation, and fatigue) for those patients receiving the mistletoe therapy in addition to the chemotherapy. 

A 2014 review of studies [20] on mistletoe therapy for breast cancer patients found that the majority of the clinical trials reviewed suggested a beneficial effect with respect to survival, improved quality of life, positive remission rate, and reduction of chemotherapy-caused side effects for breast cancer patients treated with mistletoe extracts.

A 2016 research review [21] found that mistletoe therapy for cancer patients showed “promising results” for improvement of the quality of life and reduction of fatigue in patients with cancer undergoing chemotherapy.

Research: Does Mistletoe Therapy Increase Survival?

A number of study reviews have been conducted investigating this question, with mixed results. While some studies report increased survival with mistletoe therapy, other studies have not.

A 2008 meta-analysis [22] of studies on mistletoe therapy for breast cancer patients found that mistletoe therapy (specifically Iscador) might prolong overall survival and improve the patients’ ability to cope with their illness better.

A 2009 meta-analysis [23] on mistletoe for cancer patients stated “Despite obvious limitations, and strong hints for a publication bias which limits the evidence found in this meta-analysis, one cannot ignore the fact that studies with positive effects of VA-E [Viscum album extracts] on survival of cancer patients are accumulating.”

A 2012 meta-analysis [24] suggested a moderate improvement in the survival of cancer patients receiving mistletoe therapy.

A 2014 review of studies [20] on mistletoe therapy for breast cancer patients found that the majority of the clinical trials reviewed suggested a beneficial effect with respect to survival, in addition to improved quality of life, positive remission rate, and reduction of chemotherapy-caused side effects for breast cancer patients treated with mistletoe extracts.

I was surprised to read that a 2017 German retrospective study [25] wasn’t so positive. Over 18,000 women with invasive breast cancer were included in the study and it investigated patients treated with and without mistletoe lectin in addition to standard breast cancer treatment. The study concluded that they did not observe any difference in the overall survival, recurrence-free survival, or quality of life between breast cancer patients with standard treatment and those who received both standard treatment and  mistletoe therapy. I felt I must include this data, and not only the positive studies.

The Cost of Mistletoe Therapy

In several progressive European countries including Germany, the insurance system pays for the cost of mistletoe therapy. That is definitely not the case in North America, Australia, or other non-European countries. The cost of mistletoe therapy can vary, and depends on the extract strength being used, and the frequency of administration. In the United States you can expect an IV infusion of mistletoe (if you can find a doctor to administer it) to average between $200-300 per month (but of course that’s a lot cheaper than the cost of chemotherapy.)

Possible Side Effects

Most studies found that mistletoe is generally well tolerated, adverse affects are few. [13]-[14], [26]-[27]. If side effects are experienced, they are usually minor, depend on the dose, and normally go away within a few days post-treatment. If side effects are experienced they may include some swelling, warmth, pain, redness or itchiness at the injection site. Also fatigue, mild flu-like symptoms, mild fever and diarrhea have been noted.

Contraindications and Warnings

Always consult with your chosen health professional before utilizing mistletoe in any form. It can be poisonous if you don’t know what you are doing. 

Mistletoe should not be used in combination with drugs that suppress the immune system, due to the fact that it stimulates the immune system.

Mistletoe should be used with caution by diabetics taking insulin as it may have the potential to stimulate insulin secretion. [28]

If taking antihypertensive drugs, mistletoe has been shown to lower blood pressure and may compound the effect of the drug.

If you have a known allergy to members of the Viscaceae or Loranthaceae plant families, it should definitely be avoided.

Finally, those who have seizure disorders should avoid mistletoe. If you are pregnant or breast feeding, use mistletoe with great caution and always under the supervision of a qualified doctor.

The Bottom Line

Despite obvious limitations and mixed results with many studies, it appears that positive studies on the effects of mistletoe therapy for cancer patients are accumulating. I personally know quite a few who have used mistletoe therapy as a part of their breast cancer treatments. They did not use them as the sole therapy against breast cancer, nor would I advise that. Mistletoe is not yet a proven cancer treatment and should not be used as a stand-alone treatment. However, in combination with other therapies, I believe the research and evidence shows there may be ample benefits for immunity, possible benefits for tumor regression, and certainly improved quality of life.

Interesting Tidbits

Mistletoe is believed to have been named using the Celtic word for “all-heal.”
Actress Suzanne Somers and former US president Ronald Reagan traveled to Germany to undergo mistletoe therapy for their cancers and both experienced good results. 

References:
[1] Efficacy and safety of mistletoe preparations (Viscum album) for patients with cancer diseases. A systematic review – https://pubmed.ncbi.nlm.nih.gov/19729932/

[2] Mediation of human NK-activity by components in extracts of Viscum album – https://pubmed.ncbi.nlm.nih.gov/3583510/

[3] Chemical specificity of effector cell/tumor cell bridging by a Viscum album rhamnogalacturonan enhancing cytotoxicity of human NK cells – https://www.sciencedirect.com/science/article/abs/pii/016231099090028D

[4] Biochemical characterization of a component in extracts of Viscum album enhancing human NK cytotoxicity – https://www.sciencedirect.com/science/article/abs/pii/0162310989900039

[5] Immunomodulatory effects of Viscum album extracts on natural killer cells: review of clinical trials – https://pubmed.ncbi.nlm.nih.gov/20484913/

[6] Article: White-Berry Mistletoe ( Viscum album L.) as complementary treatment in cancer: Does it help? – https://www.researchgate.net/publication/251711567_White-Berry_Mistletoe_Viscum_album_L_as_complementary_treatment_in_cancer_Does_it_help

[7] Cytotoxic activity and absence of tumor growth stimulation of standardized mistletoe extracts in human tumor models in vitro – https://pubmed.ncbi.nlm.nih.gov/17352237/

[8] Quality of life in breast cancer patients during chemotherapy and concurrent therapy with a mistletoe extract – https://www.researchgate.net/publication/45720483_Quality_of_life_in_breast_cancer_patients_during_chemotherapy_and_concurrent_therapy_with_a_mistletoe_extract

[9] Effects of Viscum album Extract Therapy in Patients with Cancer: Relation with Interleukin-6, Soluble Interleukin-6 Receptor, and Soluble gp130 – https://www.researchgate.net/publication/8541896_Effects_of_Viscum_album_Extract_Therapy_in_Patients_with_Cancer_Relation_with_Interleukin-6_Soluble_Interleukin-6_Receptor_and_Soluble_gp130

[10] Immunoactive effects of various mistletoe lectin-1 dosages in mammary carcinoma patients – https://pubmed.ncbi.nlm.nih.gov/7779151/

[11] Measurements of IL-6, soluble IL-6 receptor and soluble gp130 in sera of B-cell lymphoma patients. Does viscum album treatment affect these parameters? – https://pubmed.ncbi.nlm.nih.gov/12046687/

[12] Immunologic response to mistletoe extract (Viscum album L.) after conventional treatment in patients with operable breast cancer – https://koreauniv.pure.elsevier.com/en/publications/immunologic-response-to-mistletoe-extract-viscum-album-l-after-co

[13] Mistletoe therapy in oncology – https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003297.pub2/full#:~:text=Of%20the%2016%20trials%20investigating,patients%20during%20chemotherapy%20were%20of

[14] Viscum album L. extracts in breast and gynaecological cancers: a systematic review of clinical and preclinical research – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711058/

[15] Disappearance of an advanced adenomatous colon polyp after intratumoural injection with Viscum album (European mistletoe) extract: a case report – https://pubmed.ncbi.nlm.nih.gov/25532007/

[16] Interaction of a standardized mistletoe (Viscum album) preparation with antitumor effects of Trastuzumab in vitro – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4973521/

[17] Impact of complementary mistletoe extract treatment on quality of life in breast, ovarian and non-small cell lung cancer patients. A prospective randomized controlled clinical trial – https://pubmed.ncbi.nlm.nih.gov/15015612/

[18] Complementary cancer therapy: a systematic review of prospective clinical trials on anthroposophic mistletoe extracts – https://pubmed.ncbi.nlm.nih.gov/17507307/

[19] Additional Therapy with a Mistletoe Product during Adjuvant Chemotherapy of Breast Cancer Patients Improves Quality of Life: An Open Randomized Clinical Pilot Trial – https://www.hindawi.com/journals/ecam/2014/430518/

[20] Preclinical and Clinical Effects of Mistletoe against Breast Cancer – https://www.researchgate.net/publication/264903226_Preclinical_and_Clinical_Effects_of_Mistletoe_against_Breast_Cancer

[21] Cancer Patients’ Experiences of Using Mistletoe (Viscum album): A Qualitative Systematic Review and Synthesis – https://pubmed.ncbi.nlm.nih.gov/26684278/

[22] Individual Patient Data Meta-analysis of Survival and Psychosomatic Self-regulation from Published Prospective Controlled Cohort Studies for Long-term Therapy of Breast Cancer Patients with a Mistletoe Preparation (Iscador) – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2862937/

[23] Survival of cancer patients treated with mistletoe extract (Iscador): a systematic literature review – https://bmccancer.biomedcentral.com/articles/10.1186/1471-2407-9-451

[24] Retrolective studies on the survival of cancer patients treated with mistletoe extracts: a meta-analysis – https://pubmed.ncbi.nlm.nih.gov/22938746/

[25] Is Mistletoe Treatment Beneficial in Invasive Breast Cancer? A New Approach to an Unresolved Problem – http://ar.iiarjournals.org/content/38/3/1585.abstract

[26] Complementary cancer therapy: a systematic review of prospective clinical trials on anthroposophic mistletoe extracts – https://pubmed.ncbi.nlm.nih.gov/17507307/

[27] Review article: Influence of Viscum album L (European mistletoe) extracts on quality of life in cancer patients: a systematic review of controlled clinical studies – https://pubmed.ncbi.nlm.nih.gov/20483874/

[28] Insulin-secreting activity of the traditional antidiabetic plant Viscum album (mistletoe) – https://joe.bioscientifica.com/view/journals/joe/160/3/409.xmlMonograph: Ottawa Integrative Cancer Centre Monograph on Mistletoe – https://silo.tips/download/professional-resource-mistletoe