Overview
Questions and Answers About Coenzyme Q₁₀
Changes To This Summary (08/17/2006)
General CAM Information
Evaluation of CAM Approaches
Questions to Ask Your Health Care Provider About CAM
To Learn More About CAM

Overview

• Coenzyme Q ₁₀ is a compound that is made naturally in the body. The body uses it for cell growth and to protect cells from damage that could lead to cancer (see Question 1 ¹).



• Animal studies have shown that coenzyme Q₁₀ helps the immune system work better and makes the body better able to resist certain infections and types of cancer (see Question 5 ²).



• Clinical trials have shown that coenzyme Q₁₀ helps protect the heart from the damaging side effects of doxorubicin, a drug used to treat cancer (see Question 6 ³).



• In 3 small studies of coenzyme Q₁₀ in breast cancer patients, some patients appeared to be helped by the treatment. Weaknesses in study design and reporting, however, made it unclear if benefits were caused by the coenzyme Q₁₀ or by something else (see Question 6 ³).



• Coenzyme Q₁₀ may not mix safely with other treatments. It is important that patients tell their health care providers about all therapies they are currently using or thinking of using (see Question 7 ⁴).



• Coenzyme Q₁₀ has not been carefully tested to see if it is safe and effective. Because coenzyme Q₁₀ is sold as a dietary supplement rather than a drug, it is not regulated by the US Food and Drug Administration (see Question 8 ⁵).

Questions and Answers About Coenzyme Q₁₀

1. What is coenzyme Q₁₀?

   Coenzyme Q ₁₀ is a compound that is made naturally in the body. The Q and the 10 in coenzyme Q₁₀ refer to the groups of chemicals that make up the coenzyme. Coenzyme Q₁₀ is also known by these other names:

   • CoQ₁₀.
   • Q₁₀.
   • Vitamin Q₁₀.
   • Ubiquinone.
   • Ubidecarenone.

   A coenzyme helps an enzyme do its job. An enzyme is a protein that speeds up the rate at which natural chemical reactions take place in cells of the body. The body's cells use coenzyme Q₁₀ to make energy needed for the cells to grow and stay healthy. The body also uses coenzyme Q₁₀ as an antioxidant. An antioxidant is a substance that protects cells from chemicals called free radicals. Free radicals can damage DNA (deoxyribonucleic acid). Genes, which are pieces of DNA, tell the cells how to work in the body and when to grow and divide. Damage to DNA has been linked to some kinds of cancer. By protecting cells against free radicals, antioxidants help protect the body against cancer.

   Coenzyme Q₁₀ is found in most body tissues. The highest amounts are found in the heart, liver, kidneys, and pancreas. The lowest amounts are found in the lungs. The amount of coenzyme Q₁₀ in tissues decreases as people get older.

2. What is the history of the discovery and use of coenzyme Q₁₀ as a complementary or alternative treatment for cancer?

   Coenzyme Q₁₀ was first identified in 1957. Its chemical structure was determined in 1958. Interest in coenzyme Q₁₀ as a possible treatment for cancer began in 1961, when it was found that some cancer patients had a lower than normal amount of it in their blood. Low blood levels of coenzyme Q₁₀ have been found in patients with myeloma, lymphoma, and cancers of the breast, lung, prostate, pancreas, colon, kidney, and head and neck.

   Studies suggest that coenzyme Q₁₀ may help the immune system work better. Partly because of this, coenzyme Q₁₀ is used as adjuvant therapy for cancer. Adjuvant therapy is treatment given following the primary treatment to increase the chances of a cure.

3. What is the theory behind the claim that coenzyme Q₁₀ is useful in treating cancer?

   Coenzyme Q₁₀ may be useful in treating cancer because it boosts the immune system. Also, studies suggest that CoQ₁₀ analogs (drugs that are similar to CoQ₁₀) may prevent the growth of cancer cells directly. As an antioxidant, coenzyme Q₁₀ may help prevent cancer from developing.

   Refer to the PDQ health professional summary on Coenzyme Q10 ⁶ for more information on the theory behind the study of coenzyme Q₁₀ in the treatment of cancer.

4. How is coenzyme Q₁₀ administered?

   Coenzyme Q₁₀ is usually taken by mouth as a pill (tablet or capsule). It may also be given by injection into a vein (IV). In animal studies, coenzyme Q₁₀ is given by injection.

5. Have any preclinical (laboratory or animal) studies been conducted using coenzyme Q₁₀?

   A number of preclinical studies have been done with coenzyme Q₁₀. Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. These preclinical studies are done before any testing in humans is begun. Most laboratory studies of coenzyme Q₁₀ have looked at its chemical structure and how it works in the body. The following has been reported from preclinical studies of coenzyme Q₁₀ and cancer:

   • Animal studies found that coenzyme Q₁₀ boosts the immune system and helps the body fight certain infections and types of cancer.
   • Coenzyme Q₁₀ helped to protect the hearts of study animals that were given the anticancer drug doxorubicin, an anthracycline that can cause damage to the heart muscle.
   • Laboratory and animal studies have shown that analogs of coenzyme Q₁₀ may stop cancer cells from growing.
6. Have any clinical trials (research studies with people) of coenzyme Q₁₀ been conducted?

   There have been no well-designed clinical trials involving large numbers of patients to study the use of coenzyme Q₁₀ in cancer treatment. There have been some clinical trials with small numbers of people, but the way the studies were done and the amount of information reported made it unclear if benefits were caused by the coenzyme Q₁₀ or by something else. Most of the trials were not randomized or controlled. Randomized controlled trials give the highest level of evidence:

   • In randomized trials, volunteers are assigned randomly (by chance) to one of 2 or more groups that compare different factors related to the treatment.
   • In controlled trials, one group (called the control group) does not receive the new treatment being studied. The control group is then compared to the groups that receive the new treatment, to see if the new treatment makes a difference.

   Some research studies are published in scientific journals. Most scientific journals have experts who review research reports before they are published, to make sure that the evidence and conclusions are sound. This is called peer review. Studies published in peer-reviewed scientific journals are considered better evidence. No randomized clinical trials of coenzyme Q₁₀ as a treatment for cancer have been published in a peer-reviewed scientific journal.

   The following has been reported from studies of coenzyme Q₁₀ in people:

   Randomized trial of coenzyme Q₁₀ and doxorubicin

   A randomized trial of 20 patients looked at whether coenzyme Q₁₀ would protect the heart from the damage caused by the anthracycline drug doxorubicin. The results of this trial and others have shown that coenzyme Q₁₀ decreases the harmful effects of doxorubicin on the heart.

   Studies of coenzyme Q₁₀ as an adjuvant therapy for breast cancer

   Small studies have been done on the use of coenzyme Q₁₀ after standard treatment in patients with breast cancer:

   • In a study of coenzyme Q₁₀ in 32 breast cancer patients, it was reported that some signs and symptoms of cancer went away in 6 patients. Details were given for only 3 of the 6 patients. The researchers also reported that all the patients in the study used less pain medicine, had improved quality of life, and did not lose weight during treatment.
   
   
   
   • In a follow-up study, two patients who had breast cancer remaining after surgery were treated with high doses of coenzyme Q₁₀ for 3 to 4 months. It was reported that after treatment with high-dose coenzyme Q₁₀, the cancer was completely gone in both patients.
   
   
   
   • In a third study led by the same researchers, 3 breast cancer patients were given high-dose coenzyme Q₁₀ and followed for 3 to 5 years. The study reported that one patient had complete remission of cancer that had spread to the liver, another had remission of cancer that had spread to the chest wall, and the third had no breast cancer found after surgery.
   
   
   

   It is not clear, however, if the benefits reported in these studies were caused by coenzyme Q₁₀ therapy or something else. The studies had the following weaknesses:

   • The studies were not randomized or controlled.
   • The patients used other supplements in addition to coenzyme Q₁₀.
   • The patients received standard treatments before or during the coenzyme Q₁₀ therapy.
   • Details were not reported for all patients in the studies.

   Anecdotal reports of coenzyme Q₁₀

   Anecdotal reports are incomplete descriptions of the medical and treatment history of one or more patients. There have been anecdotal reports that coenzyme Q₁₀ has helped some cancer patients live longer, including patients with cancers of the pancreas, lung, colon, rectum, and prostate. The patients described in these reports, however, also received treatments other than coenzyme Q₁₀, including chemotherapy, radiation therapy, and surgery.

7. Have any side effects or risks been reported from coenzyme Q₁₀?

   No serious side effects have been reported from the use of coenzyme Q₁₀. The most common side effects include the following:

   • Insomnia (being unable to fall sleep or stay asleep).
   • Higher than normal levels of liver enzymes.
   • Rashes.
   • Nausea.
   • Pain in the upper part of the abdomen.
   • Dizziness.
   • Feeling sensitive to light.
   • Feeling irritable.
   • Headache.
   • Heartburn.
   • Feeling very tired.

   It is important to check with health care providers to find out if coenzyme Q₁₀ can be safely used along with other drugs. Certain drugs, such as those that are used to lower cholesterol, blood pressure, or blood sugar levels, may decrease the effects of coenzyme Q₁₀. Coenzyme Q₁₀ may change way the body uses warfarin (a drug that prevents the blood from clotting) and insulin.

   As noted in Question 1 ¹, the body uses coenzyme Q₁₀ as an antioxidant. Antioxidants protect cells from free radicals. Some conventional cancer therapies, such as anticancer drugs and radiation treatment, kill cancer cells in part by causing free radicals to form. Researchers are studying whether using coenzyme Q₁₀ along with conventional therapies has any effect, good or bad, on the way these conventional therapies work in the body.

8. Is coenzyme Q₁₀ approved by the US Food and Drug Administration (FDA) for use as a cancer treatment in the United States?

   Coenzyme Q₁₀ is sold as a dietary supplement and is not approved by the FDA for use as a cancer treatment. In the United States, dietary supplements are regulated as foods, not drugs. This means that approval by the FDA is not required before coenzyme Q₁₀ is sold, unless specific health claims are made about the supplement. Also, the way companies make coenzyme Q₁₀ is not regulated. Different batches and brands of coenzyme Q₁₀ supplements may be different from each other.

Changes To This Summary (08/17/2006)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

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 ⁷, 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: info@nccam.nih.gov

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 ⁸. It can also be accessed through NLM PubMed ⁹ 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 ¹⁰.

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 9:00 am to 4:30 pm. Deaf and hearing impaired callers with TTY equipment may call 1-800-332-8615. 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

CRC-240

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/

Glossary Terms

The area of the body that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.

Treatment given after the primary treatment to increase the chances of a cure. Adjuvant therapy may include chemotherapy, radiation therapy, hormone therapy, or biological therapy.

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

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.

A laboratory experiment using animals to study the development and progression of diseases. Animal studies also test how safe and effective new treatments are before they are tested in people.

A type of antibiotic that comes from certain types of Streptomyces bacteria. Anthracyclines are used to treat many types of cancer. Anthracyclines damage the DNA in cancer cells, causing them to die. Daunorubicin, doxorubicin, and epirubicin are anthracyclines.

A substance that protects cells from the damage caused by free radicals (unstable molecules made by the process of oxidation during normal metabolism). Free radicals may play a part in cancer, heart disease, stroke, and other diseases of aging. Antioxidants include beta-carotene, lycopene, vitamins A, C, and E, and other natural and manufactured substances.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

The force of circulating blood on the walls of the arteries. Blood pressure is taken using two measurements: systolic (measured when the heart beats, when blood pressure is at its highest) and diastolic (measured between heart beats, when blood pressure is at its lowest). Blood pressure is written with the systolic blood pressure first, followed by the diastolic blood pressure (for example 120/80).

Glandular organ located on the chest. The breast is made up of connective tissue, fat, and breast tissue that contains the glands that can make milk. Also called mammary gland.

Cancer that forms in tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

Treatment with drugs that kill cancer cells.

The muscles, bones, and joints that make up the area of the body between the neck and the abdomen.

A waxy, fat-like substance made in the liver, and found in the blood and in all cells of the body. Cholesterol is important for good health and is needed for making cell walls, tissues, hormones, vitamin D, and bile acid. Cholesterol also comes from eating foods taken from animals such as egg yolks, meat, and whole-milk dairy products. Too much cholesterol in the blood may build up in blood vessel walls, block blood flow to tissues and organs, and increase the risk of developing heart disease and stroke.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical trial.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called a clinical study.

A substance found in most tissues in the body, and in many foods. It can also be made in the laboratory. It is used by the body to produce energy for cells, and as an antioxidant. It is being studied in the treatment of cancer and in the relief of side effects caused by some cancer treatments. Also called Q10, CoQ10, vitamin Q10, and ubiquinone.

The longest part of the large intestine, which is a tube-like organ connected to the small intestine at one end and the anus at the other. The colon removes water and some nutrients and electrolytes from partially digested food. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.

In science, a substance that is made up of more than one ingredient.

In a clinical trial, the group that does not receive the new treatment being studied. This group is compared to the group that receives the new treatment, to see if the new treatment works.

A clinical study that includes a comparison (control) group. The comparison group receives a placebo, another treatment, or no treatment at all.

A currently accepted and widely used treatment for a certain type of disease, based on the results of past research. Also called conventional treatment.

To heal or restore health; a treatment to restore health.

A product that is added to the diet. A dietary supplement is taken by mouth, and usually contains one or more dietary ingredient (such as vitamin, mineral, herb, amino acid, and enzyme). Also called nutritional supplement.

Deoxyribonucleic acid. The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called deoxyribonucleic acid.

The amount of medicine taken, or radiation given, at one time.

A drug that is used to treat many types of cancer and is being studied in the treatment of other types of cancer. Doxorubicin comes from the bacterium Streptomyces peucetius. It damages DNA (the molecules inside cells that carry genetic information) and stops cells from growing. Rapidly growing tumor cells that take up doxorubicin may die. It is a type of anthracycline antitumor antibiotic. Also called doxorubicin hydrochloride, Adriamycin PFS, Adriamycin RDF, and Rubex.

Any substance, other than food, that is used to prevent, diagnose, treat or relieve symptoms of a disease or abnormal condition. Also refers to a substance that alters mood or body function, or that can be habit-forming or addictive, especially a narcotic.

A protein that speeds up chemical reactions in the body.

Food and Drug Administration. An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The FDA also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called Food and Drug Administration.

FDA. An agency in the U.S. federal government whose mission is to protect public health by making sure that food, cosmetics, and nutritional supplements are safe to use and truthfully labeled. The Food and Drug Administration also makes sure that drugs, medical devices, and equipment are safe and effective, and that blood for transfusions and transplant tissue are safe. Also called FDA.

A highly reactive chemical that often contains oxygen and is produced when molecules are split to give products that have unpaired electrons (a process called oxidation). Free radicals can damage important cellular molecules such as DNA or lipids or other parts of the cell.

The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.

Into or within a vein. I.V. usually refers to a way of giving a drug or other substance through a needle or tube inserted into a vein. Also called intravenous.

The complex group of organs and cells that defends the body against infections and other diseases.

Invasion and multiplication of germs in the body. Infections can occur in any part of the body and can spread throughout the body. The germs may be bacteria, viruses, yeast, or fungi. They can cause a fever and other problems, depending on where the infection occurs. When the body’s natural defense system is strong, it can often fight the germs and prevent infection. Some cancer treatments can weaken the natural defense system.

Use of a syringe and needle to push fluids or drugs into the body; often called a "shot."

Difficulty in going to sleep or getting enough sleep.

A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy.

One of a pair of organs in the abdomen. Kidneys remove waste from the blood (as urine), produce erythropoietin (a substance that stimulates red blood cell production), and play a role in blood pressure regulation.

Research done in a laboratory. These studies may use test tubes or animals to find out if a drug, procedure, or treatment is likely to be useful. Laboratory studies take place before any testing is done in humans.

A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.

One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.

Cancer that begins in cells of the immune system. There are two basic categories of lymphomas. One kind is Hodgkin lymphoma, which is marked by the presence of a type of cell called the Reed-Sternberg cell. The other category is non-Hodgkin lymphomas, which includes a large, diverse group of cancers of immune system cells. Non-Hodgkin lymphomas can be further divided into cancers that have an indolent (slow-growing) course and those that have an aggressive (fast-growing) course. These subtypes behave and respond to treatment differently. Both Hodgkin and non-Hodgkin lymphomas can occur in children and adults, and prognosis and treatment depend on the stage and the type of cancer.

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

A feeling of sickness or discomfort in the stomach that may come with an urge to vomit. Nausea is a side effect of some types of cancer therapy.

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.

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.

A gland in the male reproductive system. The prostate surrounds the part of the urethra (the tube that empties the bladder) just below the bladder, and produces a fluid that forms part of the semen.

A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.

The overall enjoyment of life. Many clinical trials assess the effects of cancer and its treatment on the quality of life. These studies measure aspects of an individual’s sense of well-being and ability to carry out various activities.

The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, 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 near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called radiotherapy and irradiation.

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.

The last several inches of the large intestine. The rectum ends at the anus.

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 cancer still may be in the body.

A person who has studied science, especially one who is active in a particular field of investigation.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

In medicine, treatment that experts agree is appropriate, accepted, and widely used. Health care providers are obligated to provide patients with standard therapy. Also called standard of care or best practice.

Adding nutrients to the diet.

A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

Treatment.

A group or layer of cells that work together to perform a specific function.

A drug that prevents blood from clotting. It belongs to the family of drugs called anticoagulants (blood thinners).