Clinical trial (also called clinical study) A type of research study that tests the effectiveness of new medical approaches in people. These studies test new methods of screening, prevention, diagnosis, or treatment.

Double-blinded A clinical trial in which the medical staff, the patient, and the people who analyze the results do not know the specific treatment the patient received until after the clinical trial is ended.

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Eligibility criteria Requirements designed to make sure participants in a trial are similar (such as age, type and stage of cancer, general health, and previous treatment). This ensures that study results are caused by the therapy being tested and not by other factors.

Expanded access (also called compassionate use) A way for a patient with cancer to receive a promising but not yet fully studied or approved therapy when no other treatment option exists.

Informed consent (also called consent process) The process in which patients are given important information about the clinical trial to help them decide if they wish to participate. New information that may affect a patient’s decision to continue in the trial may also be provided.

Placebo An inactive substance or treatment that looks the same as, and is administered in the same way as, an active drug or treatment being tested. The effects of the active drug or treatment are compared to the effects of the placebo.

Protocol A detailed plan that explains what a study is for, how it will be conducted, and why it is being conducted. The plan also includes information on the number of participants, who can participate, the type of treatments, how the participants will be monitored, and the information to be collected.

Randomization The process by which participants are assigned to separate groups for comparison of different treatments or interventions. Each participant has an equal chance of being assigned to any of the groups.

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

Source: Dictionary of cancer terms. National Cancer Institute Web site. http://www.cancer.gov/dictionary. Accessed February 6, 2012.