Clinical Trials Glossary

The following terms are ones often used by the Clinical Trials Office. For a complete dictionary of cancer terms, check CancerNet's Dictionary of Cancer Terms.

Acquired immune deficiency syndrome (AIDS)

AIDS is a viral disease that destroys the body's ability to fight infections, leaving the body susceptible to many other diseases. AIDS is also known as Autoimmune Immunodeficiency Syndrome.

Adjuvant chemotherapy

One or more anticancer drugs used in combination with surgery or radiation therapy as part of the treatment of cancer. Adjuvant usually means "in addition to" initial treatment. 


The loss of hair, which may include all body hair as well as scalp hair.


A condition in which a decreased number of red blood cells may cause symptoms including tiredness, shortness of breath, and weakness.


A protein produced by a plasma cell in the lymphatic system or bone marrow. An antibody binds to the specific antigen that has stimulated the immune system. Once bound, the antigen can be destroyed by other cells of the immune system.


A substance, foreign to the body, that stimulates the production of antibodies by the immune system. Antigens include foreign proteins, bacteria, viruses, pollen and other materials. 

Antiemetic agent

A drug that prevents or controls nausea and vomiting.

Benign growth

A swelling or growth that is not cancerous and does not spread from one part of the body to another.

Biological therapy

Use of biologicals (substances produced by our own cells) or biological response modifiers (substances that affect the patient's defense systems) in the treatment of cancer. 


The surgical removal of tissue for microscopic examination to aid in diagnosis.

Blood cells

Minute structures produced in the bone marrow; they consist of red blood cells, white blood cells, and platelets.

Blood count

Measurement of the number of red cells, white cells, and platelets in a sample of blood. 

Bone marrow

The inner, spongy core of bone that produces blood cells. 

Bone marrow biopsy and aspiration

The procedure by which a needle is inserted into a bone to withdraw a sample of bone marrow.

Bone marrow suppression

A decrease in the production of blood cells. Bone marrow suppression is a side effect of chemotherapy treatment in come cases

Bone marrow transplant

The infusion of bone marrow into a patient who has been treated with high dose chemotherapy or radiation therapy. Patients may use their own marrow, which in some cases has been frozen.

  • Allogeneic
    The infusion of bone marrow from one individual (donor) to another.
  • Autologous
    The infusion of a patient's own bone marrow previously removed and stored.
  • Syngeneic
    The infusion of bone marrow from one identical twin into another.

Bone scan

A picture of the bones using a radioactive dye that shows any injury, disease, or healing. This is a valuable test to determine if cancer has spread to the bone, if anticancer therapy has been successful, and if affected bony areas are healing.

Breast self-examination (BSE)

A manual self-examination of the breasts.


The insertion of a flexible, lighted tube through the mouth into the lungs to examine the lungs and airways.


A general term for more than 100 diseases characterized by abnormal and uncontrolled growth of cells. The resulting mass, or tumor, can invade and destroy surrounding normal tissues. Cancer cells from the tumor can spread through the blood or lymph to start new cancers in other parts of the body. 

Cancer in situ

The stage where the cancer is still confined to the tissue in which it started.


A substance that causes cancer. For example, nicotine in cigarettes is a carcinogen that causes lung cancer.


A type of cancer that starts in the skin or the lining of organs.

CAT scan (CT scan)

A test using computers and x-rays to create images of various parts of the body.

CCOP (Community Clinical Oncology Program)

This program links community physicians with NCI clinical research programs, so that more cancer patients can participate in clinical trials in their own communities. NCI has funded 62 CCOPs affiliated with over 200 hospitals in 34 states.

CEA (Carcinoembryonic antigen)

A blood tumor marker.


The inflammation of an area of the skin (epithelial layer).

Central venous catheter

A special intravenous tubing that is surgically inserted into a large vein near the heart and exits from the chest or abdomen. The catheter allows medications, fluids, or blood products to be given and blood samples to be taken.


Treatment with anticancer drugs.

  • Adjuvant chemotherapy
    Chemotherapy given to kill any remaining cancer cells, usually after all detectable tumor is removed by surgery or radiotherapy.
  • Combination chemotherapy
    The use of more than one drug during cancer treatment.


Persisting over a long period of time.

Clinical trial

The systematic investigation of the effects of materials or methods, according to a formal study plan and generally in a human population with a particular disease or class of diseases. In cancer research, a clinical trial generally refers to the evaluation of treatment methods such as surgery, drugs or radiation techniques, although methods of prevention, detection or diagnosis also may be the subject of such studies. 


A procedure to look at the colon or large bowel through a lighted, flexible tube.

Colony-stimulating factor (CSF)

An injectable substance used to stimulate the bone marrow to produce more cells.

Combination chemotherapy

Use of two or more anticancer drugs. 

Combination therapy

The use of two or more modes of treatment-surgery, radiotherapy, chemotherapy, immunotherapy-in combination, alternately or together, to achieve optimum results against cancer. 

Control group

In clinical studies this is a group of patients which receives standard treatment, a treatment or intervention currently being used and considered to be of proved effectiveness on the basis of past studies. Results in patients receiving newly developed treatments may then be compared to the control group. In cases where no standard treatment yet exists for a particular condition, the control group would receive no treatment. No patient is placed in a control group without treatment if there is any beneficial treatment known for that patient. 


An accumulation of fluid or semisolid material within a sac.


Characteristic of a controlled experiment in which neither the patient nor the attending physician knows whether the patient is getting one or another drug or dose. In single-blind studies, patients do not know which of several treatments they are receiving, thus preventing personal bias from influencing their reactions and study results. In either case, the treatment can be quickly identified, if necessary, by a special code.


Chemical product of the endocrine glands of the body, which, when secreted into body fluids, has a specific effect on other organs. 

Immune system

A complex network of organs, cells and specialized substances distributed throughout the body and defending it from foreign invaders that cause infection or disease. 


A form of biological therapy. An experimental method of treating cancer, using substances which stimulate the body's immune defense system.

Informed consent

The process in which a patient learns about and understands the purpose and aspects of a clinical trial and then agrees to participate. Of course, a patient may decline to participate. This process includes a document defining how much a patient must know about the potential benefits and risks of therapy before being able to agree to undergo it knowledgeably. (Informed consent is required in federally conducted, funded or regulated studies as well as by many state laws.) If a patient signs an informed consent form and enters a trial, he or she is still free to leave the trial at any time, and can receive other available medical care. 


A protein substance produced by white blood cells and other types of cells that have been exposed to certain viruses. In test animals, interferon has shown some activity against tumors. Studies of its usefulness in treating some types of human cancer are under way. One of a number of new agents available as biological therapy. 

Investigational new drug

A drug allowed by the Food and Drug Administration (FDA) to be used in clinical trials but not approved by the FDA for commercial marketing. 


An investigator is the experienced clinical researcher who prepares a protocol or treatment plan and implements it with patients. 


The transfer of disease from one part of the body to another. In cancer, metastasis is the migration of cancer cells from the original tumor site through the blood and lymph vessels to produce cancers in other tissues. Metastasis also is the term used for a secondary cancer growing at a distant site. 

Metastatic cancer

Cancer that has spread from its original site to one or more additional body sites. 

Monoclonal antibodies

One of several new substances used in biological therapy. These antibodies, all exactly alike, are mass-produced and designed to home in on target cancer cells. Monoclonal antibodies are products of new scientific techniques and may prove useful in both cancer diagnosis and treatment . 

Multimodality therapy

The combined use of more than one method of treatment, for example, surgery and chemotherapy.


A physician who is a cancer specialist. 


PDQ, supported by NCI, is a computerized database available to physicians nationwide. Geographically matrixed, it offers the latest information on standard treatments and ongoing clinical trials for each type and stage of cancer. The information is easily accessible for physicians via libraries and personal computers. 


An inactive substance resembling a medication, given for psychological effect or as a control in evaluating a medicine believed to be active. It is usually a tablet, capsule, or injection that contains a harmless substance but appears to be the same as the medicine being tested. A placebo may be compared with a new drug when no one knows if any drug or treatment will be effective. 


The outline or plan for use of an experimental procedure or experimental treatment. 

Radiation therapy

also called Radiotherapy
Treatment using X-rays, cobalt-60, radium, neutrons, or other types of cell- destroying radiation. 


Drugs being studied to try to boost the effect of radiation therapy. 

Randomized clinical trials

A study in which patients with similar traits, such as extent of disease, are chosen or selected by chance to be placed in separate groups that are comparing different treatments. Because irrelevant factors or preferences do not influence the distribution of patients, the treatment groups can be considered comparable and results of the different treatments used in different groups can be compared. (There is no way at the time for the researchers to know which of the treatments is best.) See also Clinical Trials. (It is the patient's choice to be in a randomized trial or not.)


The state of growing smaller or disappearing; used to describe the shrinkage or disappearance of a cancer. 


The decrease or disappearance of evidence of a disease; also the period during which this occurs. 

Risk/benefit ratio

The relation between the risks and benefits of a given treatment or procedure. Institutional Review Boards (IRBs) (located where the study is to take place) determine that the risks in a study are reasonable with respect to the potential benefits. It is also up to the patient to decide if it is reasonable for him or her to take part in a study. 

Side effect

A secondary and usually adverse effect, as from a drug or other treatment. For example, nausea is a side effect of some anticancer drugs. 

Single blind

See "Double blind." 


Methods used to establish the extent of a patient's disease. 

Standard treatment

A treatment or other intervention currently being used and considered to be of proved effectiveness on the basis of past studies . 

Study arm

The part or segment of a study to which a patient in a clinical trial is assigned. Each arm receives a particular treatment. 


Pertaining to treatment.

This information comes from the National Cancer Institute.