- Mistletoe is a semiparasitic plant that grows on several types of common trees such as apple, oak, pine, and elm. Mistletoe extract has been used since ancient times to treat many ailments (see Question 1).
- Mistletoe is one of the most widely studied complementary and alternative medicine therapies in people with cancer. In certain European countries, preparations made from European mistletoe are among the most prescribed drugs for patients with cancer (see Question 1).
- Mistletoe extract has been shown to kill cancer cells in the laboratory and to affect the immune system. However, there is limited evidence that mistletoe's effects on the immune system help the body fight cancer (see Question 2 and Question 3).
- Mistletoe extracts are usually given by injection under the skin or, less often, into a vein, into the pleural cavity, or into the tumor. (see Question 4).
- Animal studies have suggested that mistletoe may be useful in decreasing the side effects of standard anticancer therapy, such as chemotherapy and radiation (see Question 5).
- Several human studies using mistletoe to treat cancer have been done since the early 1960s, but major weaknesses in many of these have raised doubts about their findings (see Question 6).
- Very few harmful side effects have been reported from the use of mistletoe extract (see Question 7).
- The U.S. Food and Drug Administration (FDA) has not approved mistletoe as a treatment for cancer or any other medical condition (see Question 8).
- The FDA does not allow injectable mistletoe to be imported, sold, or used except for clinical research (see Question 8).
Questions and Answers About Mistletoe
- What is mistletoe?
Mistletoe is a semiparasitic plant that grows on several types of trees, including apple, oak, maple, elm, pine, and birch. It has been used for centuries to treat medical conditions such as epilepsy, hypertension, headaches, menopausal symptoms, infertility, arthritis, and rheumatism.
Mistletoe is one of the most widely studied complementary and alternative medicine therapies for cancer. In certain European countries, extracts made from European mistletoe are among the most prescribed therapies for cancer patients. These products are made and sold under brand names including:
- Iscador (also called Iscar).
- Isorel (also called Vysorel).
- Lektinol (also called Plenosol).
This summary discusses research done mainly with this mistletoe species.
The chemical makeup of mistletoe products varies, depending on many factors, including:
- The type of host tree on which the mistletoe plant grows.
- The time of year the plant is harvested.
- The species of mistletoe.
- Whether the extract is fermented or unfermented.
- Whether the extract is prepared with homeopathic methods.
- The company that makes the product.
Mistletoe extracts are prepared as water-based solutions or solutions of water and alcohol. Mistletoe products may be named according to the type of host tree on which the plant grows. For example, IscadorM is from apple trees, IscadorP comes from pine trees, IscadorQ is from oak trees, and IscadorU comes from elm trees. Some users believe that the type of mistletoe extract chosen should depend on the type of tumor and the sex of the patient.
- What is the history of the discovery and use of mistletoe as a complementary or alternative treatment for cancer?
Mistletoe was used by the Druids and the ancient Greeks, and appears in legend and folklore as a panacea or "cure -all". Modern interest in mistletoe as a possible treatment for cancer began in the 1920s.
Extracts of mistletoe have been shown to kill cancer cells in the laboratory and to boost the immune system (the complex group of organs and cells that defends the body against infection or disease). For this reason, mistletoe has been classified as a type of biological response modifier (a substance that stimulates the body's response to infection and disease). Extracts of mistletoe have also been shown in the laboratory to prevent the growth of new blood vessels needed for tumors to grow.
Ingredients in mistletoe that have been studied for their usefulness in treating cancer include:
- What is the theory behind the claim that mistletoe is useful in treating cancer?
Mistletoe extract is studied as a possible anticancer agent because it has been shown to:
- Have effects on the immune system.
- Kill mouse, rat, and human cancer cells in the laboratory.
- Protect the DNA in white blood cells in the laboratory, including cells that have been exposed to DNA-damaging chemotherapy drugs.
- How is mistletoe administered?
Mistletoe extracts are usually given by injection under the skin (subcutaneous). Less common ways to give mistletoe include by mouth, into a vein (intravenous or IV), into the pleural cavity, or into the tumor. In most reported studies, injections under the skin were given 2 to 3 times a week for various lengths of time.
- What preclinical (laboratory or animal) studies have been conducted using mistletoe?
Many laboratory and animal studies have been done with mistletoe, either alone or combined with other agents. Laboratory studies have suggested that mistletoe may support the immune system by increasing the number and activity of various types of white blood cells. One type of European mistletoe (IscadorQ) used in a 2004 laboratory study showed a strong anticancer effect on certain types of cancer cells but no anticancer effect on other types of cancer cells. While one laboratory study reported that mistletoe extract caused several types of human cancer cells to grow faster, this was not found in other recent lab studies.
Studies testing mistletoe's ability to stop cancer cell growth in animals have yielded mixed and inconsistent results, depending on the extract used, the dose tested, the way it was given, and the type of cancer studied. Results of a few animal studies have suggested that mistletoe may be useful in decreasing the side effects of standard anticancer therapy, such as chemotherapy and radiation therapy, and that it counteracts the effects of drugs used to suppress the immune system, such as cortisone.
- Have any clinical trials (research studies with people) been conducted using mistletoe?
Most clinical trials using mistletoe to treat cancer have been done in Europe. Most study results have been published in German. Although many of these trials have reported mistletoe to be effective, there are major weaknesses in almost all that raise doubts about their findings. Weaknesses have included small numbers of patients, incomplete patient data, lack of information about mistletoe dose, and problems with study design.
Many studies involve using mistletoe as adjuvant therapy in patients with cancer. One retrospective cohort study done between 1993 and 2000 looked at the use of a mistletoe extract (Iscador) as long-term adjuvant therapy in 800 patients treated with chemotherapy and/or radiation therapy for colorectal cancer that had not spread. The study found that patients treated with Iscador had fewer adverse events, better symptom relief, and improved disease-free survival compared to patients who did not receive Iscador as adjuvant therapy.
In 2002, the National Center for Complementary and Alternative Medicine (NCCAM), in cooperation with the National Cancer Institute (NCI), began enrolling patients for a phase I clinical trial of a mistletoe extract (Helixor A) and gemcitabine in patients with advanced solid tumors. This combination showed low toxicity and showed treatment benefits in almost half the patients. The trial is now closed and the data are being analyzed.
Before researchers can conduct clinical drug research in the United States, they must file an Investigational New Drug (IND) application with the Food and Drug Administration (FDA). The FDA does not make information public about IND applications or approvals; this information can be made public only by the applicants. At present, at least two U.S. investigators have IND approval to study mistletoe as a treatment for cancer.
- Have any side effects or risks been reported from mistletoe?
Very few serious side effects have been reported from the use of mistletoe extract products. Common side effects include soreness and inflammation at injection sites, headache, fever, and chills. A few cases of severe allergic reactions, including anaphylactic shock, have been reported.
- Is mistletoe approved by the U. S. Food and Drug Administration (FDA) for use as a cancer treatment in the United States?
The United States Food and Drug Administration (FDA) has not approved the use of mistletoe as a treatment for cancer or any other medical condition. The FDA does not allow injectable mistletoe extracts to be imported or used except for clinical research.
At this time, there is not enough evidence to recommend the use of mistletoe as a treatment for cancer except in carefully designed clinical trials. These trials will give more information about whether mistletoe can be useful in treating certain types of cancer.
Current Clinical Trials
Check NCI’s list of cancer clinical trials for cancer CAM clinical trials on mistletoe extract that are actively enrolling patients.
General information about clinical trials is available from the NCI Web site.
Changes To This Summary (02/20/2013)
Editorial changes were made to this summary.
General CAM Information
Complementary and alternative medicine (CAM)—also referred to as integrative medicine—includes a broad range of healing philosophies, approaches, and therapies. A therapy is generally called complementary when it is used in addition to conventional treatments; it is often called alternative when it is used instead of conventional treatment. (Conventional treatments are those that are widely accepted and practiced by the mainstream medical community.) Depending on how they are used, some therapies can be considered either complementary or alternative. Complementary and alternative therapies are used in an effort to prevent illness, reduce stress, prevent or reduce side effects and symptoms, or control or cure disease.
Unlike conventional treatments for cancer, complementary and alternative therapies are often not covered by insurance companies. Patients should check with their insurance provider to find out about coverage for complementary and alternative therapies.
Cancer patients considering complementary and alternative therapies should discuss this decision with their doctor, nurse, or pharmacist as they would any therapeutic approach, because some complementary and alternative therapies may interfere with their standard treatment or may be harmful when used with conventional treatment.
Evaluation of CAM Approaches
It is important that the same rigorous scientific evaluation used to assess conventional approaches be used to evaluate CAM therapies. The National Cancer Institute (NCI) and the National Center for Complementary and Alternative Medicine (NCCAM) are sponsoring a number of clinical trials (research studies) at medical centers to evaluate CAM therapies for cancer.
Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a rigorous scientific process that includes clinical trials with large numbers of patients. Less is known about the safety and effectiveness of complementary and alternative methods. Few CAM therapies have undergone rigorous evaluation. A small number of CAM therapies originally considered to be purely alternative approaches are finding a place in cancer treatment—not as cures, but as complementary therapies that may help patients feel better and recover faster. One example is acupuncture. According to a panel of experts at a National Institutes of Health (NIH) Consensus Conference in November 1997, acupuncture has been found to be effective in the management of chemotherapy-associated nausea and vomiting and in controlling pain associated with surgery. In contrast, some approaches, such as the use of laetrile, have been studied and found ineffective or potentially harmful.
The NCI Best Case Series Program, which was started in 1991, is one way CAM approaches that are being used in practice are being investigated. The program is overseen by the NCI’s Office of Cancer Complementary and Alternative Medicine (OCCAM). Health care professionals who offer alternative cancer therapies submit their patients’ medical records and related materials to OCCAM. OCCAM conducts a critical review of the materials and develops follow-up research strategies for approaches deemed to warrant NCI-initiated research.
Questions to Ask Your Health Care Provider About CAM
When considering complementary and alternative therapies, patients should ask their health care provider the following questions:
- What side effects can be expected?
- What are the risks associated with this therapy?
- Do the known benefits outweigh the risks?
- What benefits can be expected from this therapy?
- Will the therapy interfere with conventional treatment?
- Is this therapy part of a clinical trial?
- If so, who is sponsoring the trial?
- Will the therapy be covered by health insurance?
To Learn More About CAM
National Center for Complementary and Alternative Medicine (NCCAM)
The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.
- NCCAM Clearinghouse
- Post Office Box 7923 Gaithersburg, MD 20898–7923
- Telephone: 1–888–644–6226 (toll free) 301–519–3153 (for International callers)
- TTY (for deaf and hard of hearing callers): 1–866–464–3615
- Fax: 1–866–464–3616
- E-mail: email@example.com
- Web site: http://nccam.nih.gov
CAM on PubMed
NCCAM and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the Web sites of over 1,800 journals, allowing users to view full-text articles. (A subscription or other fee may be required to access full-text articles.) CAM on PubMed is available through the NCCAM Web site. It can also be accessed through NLM PubMed bibliographic database by selecting the "Limits" tab and choosing "Complementary Medicine" as a subset.
Office of Cancer Complementary and Alternative Medicine
The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via the NCI Web site.
National Cancer Institute (NCI) Cancer Information Service
U.S. residents may call the NCI Cancer Information Service toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 8:00 am to 8:00 pm. A trained Cancer Information Specialist is available to answer your questions.
Food and Drug Administration
The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.
- Food and Drug Administration
- 5600 Fishers Lane
- Rockville, MD 20857
- Telephone: 1–888–463–6332 (toll free)
- Web site: http://www.fda.gov/
Federal Trade Commission
The Federal Trade Commission (FTC) enforces consumer protection laws. Publications available from the FTC include:
- Who Cares: Sources of Information About Health Care Products and Services
- Fraudulent Health Claims: Don’t Be Fooled
- Consumer Response Center
- Federal Trade Commission
- Washington, DC 20580
- Telephone: 1-877-FTC-HELP (1-877-382-4357) (toll free)
- TTY (for deaf and hearing impaired callers): 202-326-2502
- Web site: http://www.ftc.gov/
PDQ is a comprehensive cancer database available on NCI's Web site.
PDQ is the National Cancer Institute's (NCI's) comprehensive cancer information database. Most of the information contained in PDQ is available online at NCI's Web site. PDQ is provided as a service of the NCI. The NCI is part of the National Institutes of Health, the federal government's focal point for biomedical research.
PDQ contains cancer information summaries.
The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries are available in two versions. The health professional versions provide detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions provide current and accurate cancer information.
Images in the PDQ summaries are used with permission of the author(s), artist, and/or publisher for use within the PDQ summaries only. Permission to use images outside the context of PDQ information must be obtained from the owner(s) and cannot be granted by the National Cancer Institute. Information about using the illustrations in the PDQ summaries, along with many other cancer-related images, are available in Visuals Online, a collection of over 2,000 scientific images.
The PDQ cancer information summaries are developed by cancer experts and reviewed regularly.
Editorial Boards made up of experts in oncology and related specialties are responsible for writing and maintaining the cancer information summaries. The summaries are reviewed regularly and changes are made as new information becomes available. The date on each summary ("Date Last Modified") indicates the time of the most recent change.
PDQ also contains information on clinical trials.
A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.
Listings of clinical trials are included in PDQ and are available online at NCI's Web site. Descriptions of the trials are available in health professional and patient versions. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237).