Overview
General Information
History
Laboratory/Animal/Preclinical Studies
Human/Clinical Studies
Adverse Effects
Levels of Evidence
Glossary of Terms
References
For More Information

Overview

This complementary and alternative medicine (CAM) information summary provides an overview of the use of coenzyme Q₁₀ in cancer therapy. The summary includes a history of coenzyme Q₁₀ research, a review of laboratory studies, and data from investigations involving human subjects. Although several naturally occurring forms of coenzyme Q have been identified, Q₁₀ is the predominant form found in humans and most mammals, and it is the form most studied for therapeutic potential. Thus, it will be the only form of coenzyme Q discussed in this CAM summary. A glossary of scientific terms used in the summary appears just before the references. Terms defined in the glossary are marked in the text by hypertext links.

This summary contains the following key information:

• Coenzyme Q₁₀ is made naturally by the human body.
• Coenzyme Q₁₀ helps cells to produce energy, and it acts as an antioxidant.
• Coenzyme Q₁₀ has shown an ability to stimulate the immune system and to protect the heart from damage caused by certain chemotherapy drugs.
• Low blood levels of coenzyme Q₁₀ have been detected in patients with some types of cancer.
• No report of a randomized clinical trial of coenzyme Q₁₀ as a treatment for cancer has been published in a peer-reviewed, scientific journal.
• Coenzyme Q₁₀ is marketed in the United States as a dietary supplement.

General Information

Coenzyme Q₁₀ (also known as Co Q₁₀, Q₁₀, vitamin Q₁₀, ubiquinone, or ubidecarenone) is a benzoquinone compound synthesized naturally by the human body. The "Q" and the "10" in the name refer to the quinone chemical group and the 10 isoprenyl chemical subunits, respectively, that are part of this compound's structure. The term "coenzyme" denotes it as an organic (contains carbon atoms), nonprotein molecule necessary for the proper functioning of its protein partner (an enzyme or an enzyme complex). Coenzyme Q₁₀ is used by cells of the body in a process known variously as aerobic respiration, aerobic metabolism, oxidative metabolism, or cell respiration. Through this process, energy for cell growth and maintenance is created inside cells in compartments called mitochondria.[reviewed in 1-4] Coenzyme Q₁₀ is also used by the body as an endogenous antioxidant.[reviewed in 1,2,4,5,7-9] An antioxidant is a substance that protects cells from free radicals, which are highly reactive chemicals, often containing oxygen atoms, capable of damaging important cellular components such as DNA and lipids. In addition, the plasma level of coenzyme Q₁₀ has been used, in studies, as a measure of oxidative stress (a situation in which normal antioxidant levels are reduced).[10,11]

Coenzyme Q₁₀ is present in most tissues, but the highest concentrations are found in the heart, the liver, the kidneys, and the pancreas.[6] The lowest concentration is found in the lungs.[6] Tissue levels of this compound decrease as people age, due to increased requirements, decreased production,[6] or insufficient intake of the chemical precursors needed for synthesis.[reviewed in 12] In humans, normal blood levels of coenzyme Q₁₀ have been defined variably, with reported values ranging from 0.30 to 3.84 micrograms per milliliter.[13,14,reviewed in 2,4]

Given the importance of coenzyme Q₁₀ to optimal cellular energy production, use of this compound as a treatment for diseases other than cancer has been explored. Most of these investigations have focused on coenzyme Q₁₀ as a treatment for cardiovascular disease.[15,reviewed in 2,4] In patients with cancer, coenzyme Q₁₀ has been shown to protect the heart from anthracycline-induced cardiotoxicity (anthracyclines are a family of chemotherapy drugs, including doxorubicin, that have the potential to damage the heart) [3,16-18] and to stimulate the immune system.[19, reviewed in 20] Stimulation of the immune system by this compound has also been observed in animal studies and in humans without cancer.[21-27] In part because of its immunostimulatory potential, coenzyme Q₁₀ has been used as an adjuvant therapy in patients with various types of cancer.[17,28,29,30, reviewed in 20,31-33]

While coenzyme Q₁₀ may show indirect anticancer activity through its effect(s) on the immune system, there is evidence to suggest that analogs of this compound can suppress cancer growth directly. Analogs of coenzyme Q₁₀ have been shown to inhibit the proliferation of cancer cells in vitro and the growth of cancer cells transplanted into rats and mice.[12,34] In view of these findings, it has been proposed that analogs of coenzyme Q₁₀ may function as antimetabolites to disrupt normal biochemical reactions that are required for cell growth and/or survival and, thus, that they may be useful for short periods of time as chemotherapeutic agents.[12,34]

Several companies distribute coenzyme Q₁₀ as a dietary supplement. In the United States, dietary supplements are regulated as foods not drugs. Therefore, premarket evaluation and approval by the Food and Drug Administration (FDA) are not required unless specific disease prevention or treatment claims are made. Because dietary supplements are not formally reviewed for manufacturing consistency, there may be considerable variation from lot to lot.

To conduct clinical drug research in the United States, researchers must file an Investigational New Drug (IND) application with the FDA. The IND application process is highly confidential, and IND information can be disclosed only by the applicants. To date, no investigators have announced that they have applied for an IND to study coenzyme Q₁₀ as a treatment for cancer.

In animal studies, coenzyme Q₁₀ has been administered by injection (intravenous, intraperitoneal, intramuscular, or subcutaneous). In humans, it is usually taken orally as a pill (tablet or capsule), but intravenous infusions have been given.[4] Coenzyme Q₁₀ is absorbed best with fat; therefore, lipid preparations are better absorbed than the purified compound.[reviewed in 2,4] In human studies, supplementation doses and administration schedules have varied, but usually have been in the range of 90 to 390 milligrams per day.

History

Coenzyme Q₁₀ was first isolated in 1957,[reviewed in 2] and its chemical structure (benzoquinone compound) was determined in 1958.[reviewed in 13] Interest in coenzyme Q₁₀ as a therapeutic agent in cancer began in 1961, when a deficiency was noted in the blood of both Swedish and American cancer patients, especially in the blood of patients with breast cancer.[13, reviewed in 30,32] A subsequent study showed a statistically significant relationship between the level of plasma coenzyme Q₁₀ deficiency and breast cancer prognosis.[14] Low blood levels of this compound have been reported in patients with malignancies other than breast cancer, including myeloma, lymphoma, and cancers of the lung, prostate, pancreas, colon, kidney, and head and neck.[12,13 reviewed in 31] Furthermore, decreased levels of coenzyme Q₁₀ have been detected in malignant human tissue,[35-39] but increased levels have been reported as well.[35]

A large amount of laboratory and animal data on coenzyme Q₁₀ has accumulated since 1962.[reviewed in 13] Research into cellular energy producing mechanisms that involve this compound was awarded the Nobel Prize in chemistry in 1978. Some of the accumulated data show that coenzyme Q₁₀ stimulates animal immune systems, leading to higher antibody levels,[21] greater numbers and/or activities of macrophages and T cells (T lymphocytes),[21,23] and increased resistance to infection.[24-26] Coenzyme Q₁₀ has also been reported to increase IgG (immunoglobulin G) antibody levels and to increase the CD4 to CD8 T-cell ratio in humans.[19,22,27] CD4 and CD8 are proteins found on the surface of T cells, with CD4 and CD8 identifying "helper" T cells and "cytotoxic" T cells, respectively; decreased CD4 to CD8 T-cell ratios have been reported for cancer patients.[40,41] Research subsequently delineated the antioxidant properties of coenzyme Q₁₀.[10,11, reviewed in 1,4,6]

Proposed mechanisms of action for coenzyme Q₁₀ that are relevant to cancer include its essential function in cellular energy production and its stimulation of the immune system (the two of which may be related), as well as its role as an antioxidant. Coenzyme Q₁₀ is essential to aerobic energy production,[reviewed in 1-3] and it has been suggested that increased cellular energy may lead to increased antibody synthesis in B cells (B lymphocytes).[12,19] As noted previously (General Information section), coenzyme Q₁₀ can also behave as an antioxidant.[reviewed in 1,2,4-9] In this capacity, coenzyme Q₁₀ is thought to stabilize cell membranes (lipid-containing structures essential to maintaining cell integrity) and to prevent free radical damage to other important cellular components.[reviewed in 1,2,6,9] Free radical damage to DNA (and possibly to other cellular molecules) may be a factor in cancer development.[reviewed in 7,10,38,42-45]

Laboratory/Animal/Preclinical Studies

Laboratory work on coenzyme Q₁₀ has focused primarily on its structure and its function in cell respiration. Studies in animals have demonstrated that coenzyme Q₁₀ is capable of stimulating the immune system, with treated animals showing increased resistance to protozoal infections [25,26] and to viral and chemically induced neoplasia.[24-26, reviewed in 13] Early studies of coenzyme Q₁₀ showed increased hematopoiesis (the formation of new blood cells) in monkeys,[reviewed in 13,17] rabbits,[46] and poultry.[reviewed in 17] Coenzyme Q₁₀ demonstrated a protective effect on the heart muscle of mice, rats, and rabbits given the anthracycline anticancer drug doxorubicin.[47-52] Although another study confirmed this protective effect with intraperitoneal administration of doxorubicin in mice, it failed to demonstrate a protective effect when the anthracycline was given intravenously, which is the route of administration in humans.[53] Researchers in one study sounded a cautionary note when they found that coadministration of coenzyme Q₁₀ and radiation therapy decreased the effectiveness of the radiotherapy.[54] In this study, mice inoculated with human small cell lung cancer cells (a xenograft study), and then given coenzyme Q₁₀ and single-dose radiation therapy, showed substantially less inhibition of tumor growth than mice in the control group that were treated with radiation therapy alone. Since radiation leads to the production of free radicals, and since antioxidants protect against free radical damage, the effect in this study might be explained by coenzyme Q₁₀ acting as an antioxidant. As noted previously (General Information section), there is some evidence from laboratory and animal studies that analogs of coenzyme Q₁₀ may exhibit direct anticancer activity.[12,34]

Human/Clinical Studies

The use of coenzyme Q₁₀ as a treatment for cancer in humans has been investigated in only a limited manner. With the exception of a single randomized trial,[18] which involved 20 patients and tested the ability of coenzyme Q₁₀ to reduce the cardiotoxicity caused by anthracycline drugs, the studies that have been published consist of anecdotal reports, case reports, case series, and uncontrolled clinical studies.[3,16,17,28- 30, reviewed in 20,31-33]

In view of the promising results from animal studies, coenzyme Q₁₀ was tested as a protective agent against the cardiac toxicity observed in cancer patients treated with the anthracycline drug doxorubicin. It has been postulated that doxorubicin interferes with energy generating biochemical reactions that involve coenzyme Q₁₀ in heart muscle mitochondria and that this interference can be overcome by coenzyme Q₁₀ supplementation.[16,52,55] Studies with adults and children, including the aforementioned randomized trial, have confirmed the decrease in cardiac toxicity observed in animal studies.[3,16-18]

The potential of coenzyme Q₁₀ as an adjuvant therapy for cancer has also been explored. In view of observations that blood levels of coenzyme Q₁₀ are frequently reduced in cancer patients,[12,13, reviewed in 30-32] supplementation with this compound has been tested in patients undergoing conventional treatment. An open-label (nonblinded), uncontrolled clinical study in Denmark followed 32 breast cancer patients for 18 months.[28] The disease in these patients had spread to the axillary lymph nodes, and an unreported number had distant metastases. The patients received antioxidant supplementation (vitamin C, vitamin E, and beta-carotene), other vitamins and trace minerals, essential fatty acids, and coenzyme Q₁₀ (at a dose of 90 milligrams per day), in addition to standard therapy (surgery, radiation therapy, and chemotherapy, with or without tamoxifen). The patients were seen every 3 months to monitor disease status (progressive disease or recurrence), and, if there was a suspicion of recurrence, mammography, bone scan, x-ray, or biopsy was performed. The survival rate for the study period was one hundred percent (four deaths were expected). Six patients were reported to show some evidence of remission; however, incomplete clinical data were provided, and information suggestive of remission was presented for only three of the six patients. None of the six patients had evidence of further metastases. For all 32 patients, decreased use of painkillers, improved quality of life, and an absence of weight loss were reported. Whether painkiller use and quality of life were measured objectively (e.g., from pharmacy records and validated questionnaires, respectively) or subjectively (from patient self-reports) was not specified.

In a follow-up study, one of the six patients with a reported remission and a new patient were treated for several months with higher doses of coenzyme Q₁₀ (390 and 300 milligrams per day, respectively).[29] Surgical removal of the primary breast tumor in both patients had been incomplete. After 3 to 4 months of high-level coenzyme Q₁₀ supplementation, both patients appeared to experience complete regression of their residual breast tumors (assessed by clinical examination and mammography). It should be noted that a different patient identifier was used in the follow-up study for the patient who had participated in the original study. Therefore, it is impossible to determine which of the six patients with a reported remission took part in the follow-up study. In the follow-up study report, the researchers noted that all 32 patients from the original study remained alive at 24 months of observation, whereas six deaths had been expected.[29]

In another report by the same investigators, three breast cancer patients were followed for a total of 3 to 5 years on high-dose coenzyme Q₁₀ (390 milligrams per day).[30] One patient had complete remission of liver metastases (determined by clinical examination and ultrasonography ), another had remission of a tumor that had spread to the chest wall (determined by clinical examination and chest X-ray), and the third patient had no microscopic evidence of remaining tumor after a mastectomy (determined by biopsy of the tumor bed).

All three of the above-mentioned human studies [28-30] had important design flaws that could have influenced their outcome. Study weaknesses include the absence of a control group (i.e., all patients received coenzyme Q₁₀), possible selection bias in the follow-up investigations, and multiple confounding variables (i.e., the patients received a variety of supplements in addition to coenzyme Q₁₀, and they received standard therapy either during or immediately before supplementation with coenzyme Q₁₀). Thus, it is impossible to determine whether any of the beneficial results was directly related to coenzyme Q₁₀ therapy.

Anecdotal reports of coenzyme Q₁₀ lengthening the survival of patients with pancreatic, lung, rectal, laryngeal, colon, and prostate cancers also exist in the peer-reviewed, scientific literature.[17] The patients described in these reports also received therapies other than coenzyme Q₁₀, including chemotherapy, radiation therapy, and surgery.

Adverse Effects

No serious toxicity associated with the use of coenzyme Q₁₀ has been reported.[reviewed in 2,4,33,56] Doses of 100 milligrams per day or higher have caused mild insomnia in some individuals.[reviewed in 2] Liver enzyme elevation has been detected in patients taking doses of 300 milligrams per day for extended periods of time, but no liver toxicity has been reported.[reviewed in 2] Researchers in one cardiovascular study reported that coenzyme Q₁₀ caused rashes, nausea, and epigastric (upper abdominal) pain that required withdrawal of a small number of patients from the study.[15] Other reported side effects have included dizziness, photophobia (abnormal visual sensitivity to light), irritability,[15] headache, heartburn, and fatigue.[57]

Certain lipid-lowering drugs, such as the "statins" (lovastatin, pravastatin, and simvastatin) and gemfibrozil, as well as oral agents that lower blood sugar, such as glyburide and tolazamide, cause a decrease in serum levels of coenzyme Q₁₀ and reduce the effects of coenzyme Q₁₀ supplementation.[58,59, reviewed in 2,60] Beta-blockers (drugs that slow the heart rate and lower blood pressure) can inhibit coenzyme Q₁₀-dependent enzyme reactions.[reviewed in 2] The contractile force of the heart in patients with high blood pressure can be increased by coenzyme Q₁₀ administration.[reviewed in 2] Coenzyme Q₁₀ can reduce the body's response to the anticoagulant drug warfarin.[reviewed in 60] Finally, coenzyme Q₁₀ can decrease insulin requirements in individuals with diabetes.[reviewed in 60]

Levels of Evidence for Human Studies of Cancer Complementary and Alternative Medicine

To assist readers in evaluating the results of human studies of CAM treatments for cancer, the strength of the evidence (i.e., the "levels of evidence") associated with each type of treatment is provided whenever possible. To qualify for a levels of evidence analysis, a study must 1) be published in a peer-reviewed, scientific journal; 2) report on a therapeutic outcome(s), such as tumor response, improvement in survival, or measured improvement in quality of life; and 3) describe clinical findings in sufficient detail that a meaningful evaluation can be made. Separate levels of evidence scores are assigned to qualifying human studies on the basis of statistical strength of the study design and scientific strength of the treatment outcomes (i.e., endpoints) measured. The resulting two scores are then combined to produce an overall score. A table showing the levels of evidence scores for qualifying human studies cited in this summary is presented below. For an explanation of the scores and additional information about levels of evidence analysis of CAM treatments for cancer, please click on the following link: Levels of Evidence Analysis for Human Studies of Cancer Complementary and Alternative Medicine.

Glossary of Terms

adjuvant therapy (AD-joo-vant): Treatment given after the primary treatment to increase the chances of a cure. Adjuvant therapy may include chemotherapy, radiation therapy, or hormone therapy.

aerobic: In biochemistry, reactions that need oxygen to happen or happen when oxygen is present.

aerobic metabolism: A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also known as aerobic respiration, oxidative metabolism, or cell respiration.

aerobic respiration: A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also known as oxidative metabolism, cell respiration, or aerobic metabolism.

analog: In chemistry, a substance that is similar, but not identical, to another.

anecdotal report: An incomplete description of the medical and treatment history of one or more patients. Anecdotal reports may be published in places other than peer-reviewed, scientific journals.

animal model: An animal with a disease either the same as or like a disease in humans. Animal models are used to study the development and progression of diseases and to test new treatments before they are given to humans. Animals with transplanted human cancers or other tissues are called xenograft models.

anthracycline: A member of a family of anticancer drugs that are also antibiotics.

antibody (AN-tih-BOD-ee): A type of protein made by certain white blood cells in response to a foreign substance (antigen). Each antibody can bind to only a specific antigen. The purpose of this binding is to help destroy the antigen. Antibodies can work in several ways, depending on the nature of the antigen. Some antibodies destroy antigens directly. Others make it easier for white blood cells to destroy the antigen.

anticoagulant: A drug that helps prevent blood clots from forming. Also called a blood thinner.

antimetabolite: A chemical that is very similar to one required in a normal biochemical reaction in cells. Antimetabolites can stop or slow down the reaction.

antioxidant: A substance that prevents damage caused by free radicals. Free radicals are highly reactive chemicals that often contain oxygen. They are produced when molecules are split to give products that have unpaired electrons. This process is called oxidation.

axillary lymph nodes: Lymph nodes found in the armpit that drain the lymph channels from the breast.

B cells: White blood cells that develop from bone marrow and produce antibodies. Also called B lymphocytes.

biopsy (BY-ahp-see): The removal of cells or tissues for examination under a microscope. When only a sample of tissue is removed, the procedure is called an incisional biopsy or core biopsy. When an entire tumor or lesion is removed, the procedure is called an excisional biopsy. When a sample of tissue or fluid is removed with a needle, the procedure is called a needle biopsy or fine-needle aspiration.

bone scan: A technique to create images of bones on a computer screen or on film. A small amount of radioactive material is injected into a blood vessel and travels through the bloodstream; it collects in the bones and is detected by a scanner.

cardiac: Having to do with the heart.

cardiotoxicity: Toxicity that affects the heart.

cardiovascular: Having to do with the heart and blood vessels.

case report: A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin).

case series: A group or series of case reports involving patients who were given similar treatment. Reports of case series usually contain detailed information about the individual patients. This includes demographic information (for example, age, gender, ethnic origin) and information on diagnosis, treatment, response to treatment, and follow-up after treatment.

catechol: A chemical originally isolated from a type of mimosa tree. Catechol is used as an astringent, an antiseptic, and in photography, electroplating, and making other chemicals. It can also be man-made.

cell respiration: A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also known as oxidative metabolism or aerobic metabolism, or aerobic respiration.

chemotherapy (kee-mo-THER-a-pee): Treatment with anticancer drugs.

complementary and alternative medicine: CAM. Forms of treatment that are used in addition to (complementary) or instead of (alternative) standard treatments. These practices are not considered standard medical approaches. CAM includes dietary supplements, megadose vitamins, herbal preparations, special teas, massage therapy, magnet therapy, spiritual healing, and meditation.

cytotoxic T cells: A type of white blood cell that can directly destroy specific cells. T cells can be separated from other blood cells, grown in the laboratory, and then given to a patient to destroy tumor cells. Certain cytokines can also be given to a patient to help form cytotoxic T cells in the patient's body.

diabetes (dye-a-BEE-teez): A disease in which the body does not properly control the amount of sugar in the blood. As a result, the level of sugar in the blood is too high. This disease occurs when the body does not produce enough insulin or does not use it properly.

doxorubicin: An anticancer drug that belongs to the family of drugs called antitumor antibiotics. It is an anthracycline.

endogenous: Produced inside an organism or cell. The opposite is external (exogenous) production.

enzyme: A protein that speeds up chemical reactions in the body.

epigastric: Having to do with the upper middle area of the abdomen.

free radicals: Highly reactive chemicals that often contain oxygen and are produced when molecules are split to give products that have unpaired electrons. This process is called oxidation. Free radicals can damage important cellular molecules such as DNA or lipids or other parts of the cell.

hematopoiesis: The forming of new blood cells.

immunoglobulin: A protein that acts as an antibody.

in vitro: In the laboratory (outside the body). The opposite of in vivo (in the body).

infusion: A method of putting fluids, including drugs, into the bloodstream. Also called intravenous infusion.

insomnia: Difficulty in going to sleep or getting enough sleep.

intramuscular: IM. Within or into muscle.

intraperitoneal (IN-tra-per-ih-toe-NEE-al): IP. Within the peritoneal cavity (the area that contains the abdominal organs).

intravenous (in-tra-VEE-nus): IV. Into a vein.

laryngeal (lair-IN-jee-al): Having to do with the larynx.

lipid: Fat.

lymphocyte (LIM-fo-site): A white blood cell. Lymphocytes have a number of roles in the immune system, including the production of antibodies and other substances that fight infection and diseases.

lymphoma (lim-FO-ma): Cancer that arises in cells of the lymphatic system.

macrophage: A type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells.

malignant (ma-LIG-nant): Cancerous; a growth with a tendency to invade and destroy nearby tissue and spread to other parts of the body.

mammography (mam-OG-ra-fee): The use of x-rays to create a picture of the breast.

mastectomy (mas-TEK-toe-mee): Surgery to remove the breast (or as much of the breast tissue as possible).

metastasis (meh-TAS-ta-sis): The spread of cancer from one part of the body to another. Tumors formed from cells that have spread are called "secondary tumors" and contain cells that are like those in the original (primary) tumor. The plural is metastases.

mitochondria: Parts of a cell where aerobic production (also known as cell respiration) takes place.

molecule: A chemical made up of two or more atoms. The atoms in a molecule can be the same (an oxygen molecule has two oxygen atoms) or different (a water molecule has two hydrogen atoms and one oxygen atom). Biological molecules, such as proteins and DNA, can be made up of many thousands of atoms.

myeloma: Cancer that arises in plasma cells, a type of white blood cell.

nasal: By or having to do with the nose.

neoplasia (NEE-o-PLAY-zha): Abnormal and uncontrolled cell growth.

nonblinded: Describes a clinical trial or other experiment in which the researchers know what treatments are being given to each study subject or experimental group. If human subjects are involved, they know what treatments they are receiving.

oral: By or having to do with the mouth.

oxidative metabolism: A chemical process in which oxygen is used to make energy from carbohydrates (sugars). Also known as aerobic respiration, cell respiration, or aerobic metabolism.

oxidative stress: A condition in which antioxidant levels are lower than normal. Antioxidant levels are usually measured in blood plasma.

pancreas: A glandular organ located in the abdomen. It makes pancreatic juices, which contain enzymes that aid in digestion, and it produces several hormones, including insulin. The pancreas is surrounded by the stomach, intestines, and other organs.

pancreatic: Having to do with the pancreas.

photophobia: A condition in which the eyes are more sensitive to light than normal.

plasma (PLAS-ma): The clear, yellowish, fluid part of the blood that carries the blood cells. The proteins that form blood clots are in plasma.

prognosis (prog-NO-sis): The likely outcome or course of a disease; the chance of recovery or recurrence.

progressive disease: Cancer that is increasing in scope or severity.

protozoal: Having to do with the simplest organisms in the animal kingdom. Protozoa are single-cell organisms, such as ameba, and are different from bacteria, which are not members of the animal kingdom. Some protozoa can be seen without a microscope.

ptosis: Drooping of the upper eyelid.

quality of life: The overall enjoyment of life. Many clinical trials measure aspects of an individual's sense of well-being and ability to perform various tasks to assess the effects of cancer and its treatment on the quality of life.

radiation therapy (ray-dee-AY-shun): The use of high-energy radiation from x-rays, gamma rays, neutrons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body in the area near cancer cells (internal radiation therapy, implant radiation, or brachytherapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that circulates throughout the body. Also called radiotherapy.

randomized clinical trial: A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

rectal: By or having to do with the rectum. The rectum is the last 8 to 10 inches of the large intestine and ends at the anus.

recurrence: The return of cancer, at the same site as the original (primary) tumor or in another location, after the tumor had disappeared.

regression: A decrease in the size of a tumor, or in the extent of cancer in the body.

remission: A decrease in or disappearance of signs and symptoms of cancer. In partial remission, some, but not all, signs and symptoms of cancer have disappeared. In complete remission, all signs and symptoms of cancer have disappeared, although there still may be cancer in the body.

selection bias: An error in choosing the individuals or groups to take part in a study. Ideally, the subjects in a study should be very similar to one another and to the larger population (for example, all individuals with the same disease or condition) from which they are drawn. If there are important differences, the results of the study may not be valid.

serum: The clear liquid part of the blood that remains after blood cells and clotting proteins have been removed.

small cell lung cancer: A type of lung cancer in which the cells appear small and round when viewed under the microscope. Also called oat cell lung cancer.

subcutaneous: Beneath the skin.

T cell: One type of white blood cell that attacks virus-infected cells, foreign cells, and cancer cells. T cells also produce a number of substances that regulate the immune response.

tamoxifen: An anticancer drug that belongs to the family of drugs called antiestrogens. Tamoxifen blocks the effects of the hormone estrogen in the body. It is used to prevent or delay the return of breast cancer or to control its spread.

therapeutic: Used to treat disease and help healing take place.

ultrasonography (UL-tra-son-OG-ra-fee): A procedure in which sound waves (called ultrasound) are bounced off tissues and the echoes are converted to a picture (sonogram).

uncontrolled study: A clinical study that lacks a comparison (i.e., a control) group.

warfarin: A drug that prevents blood from clotting. Also called an anticoagulant (blood thinner).

xenograft: The cells of one species transplanted to another species.

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For More Information

More information on CAM therapies is available at:

• The National Center for Complementary and Alternative Medicine (NCCAM)
  (URL: http://nccam.nih.gov/)

• The National Cancer Institute Office of Cancer Complementary and Alternative Medicine
  (URL: http://www3.cancer.gov/occam)

• CAM on PubMed, a special subset of the PubMed scientific literature database created through a partnership between NCCAM and the National Library of Medicine
  (URL: www.nlm.nih.gov/nccam/camonpubmed.html

Additional information about CAM and cancer can be found in the "Cancer Facts" sheet Questions and Answers About Complementary and Alternative Medicine in Cancer Treatment.

Important: This information is intended mainly for use by doctors and other health care professionals. If you have questions about this topic, you can ask your doctor, or call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).