Glossary of Clinical Trial Basic Terminology

Arm – The treatment regimen to which a patient is assigned within a study

Assent – The agreement by a minor child, who is too young to give informed consent but old enough to have some understanding of the decision, to participate in a study

Control – The group who undergoes no intervention or a standard intervention to which the group undergoing the new intervention is compared

Cohort – A collection of patients grouped together based upon certain clinical or biological features.

Comparative – A trial which compares two or more interventions to determine which is superior

Data and Safety Monitoring – Interim analysis of the clinical trial data by an independent group other than the study investigators; if there is excessive toxicity of a treatment or one treatment is clearly superior or inferior to another, the study may be modified or closed early

Double-blind – Neither the investigator nor the patient know which experimental or control treatment the patient is receiving; this helps to prevent bias when determining a patient’s response to the treatment

Dose-Limiting Toxicity (DLT) – The particular toxicity, or side effect, that limits the dose that may be given to patients

Efficacy – How well an intervention works

Eligibility – The criteria a patient must meet to be enrolled in a study

Endpoint – The result that is being evaluated by the study (e.g. survival, disease reduction, quality of life)

Escalation – Increasing a dose of a medication based on clinical and/or biological response and/or side effects

Hypothesis – The rationale for the study; why it is believed that the new intervention will be effective and what is thought the result of the study will be before the study is done

Informed Consent – Agreement to participate in a study following education of the patient (or parent of a minor child) regarding possible risks and benefits of participation in the study

Institutional Review Board (IRB) – A group of individuals from different disciplines (e.g. medicine, law, ethics) who need to approve each study before it is carried out at an institution , then monitor the progress of the study, assuring all federal regulations and ethical considerations for patient protection are met

Interim Analysis – Evaluation of preliminary results by analyzing study data while the study is still ongoing; if there is excessive toxicity of a treatment or one treatment is clearly superior or inferior to another, the study may be modified or closed early

Late Effects – Long-term side effects of a treatment on patients which may not become apparent until long after the treatment is completed

Maximum Tolerated Dose (MTD) – The highest dose of a drug, or other intervention, that is tolerated by patients before reaching a dose-limiting toxicity (see above)

Non-comparative - A study where there may be one or more treatment groups, but no direct comparison regarding effectiveness between treatment groups can be made

Pharmacokinetics – How and at what rate a drug is metabolized (broken down) and excreted (leaves the body) in patients

Placebo – A drug that has no activity, but may be used as a control treatment for comparison when evaluating a new drug

Protocol – The detailed plan of how a study is conducted and/or how a treatment is given

Randomize – Assign patients to a particular intervention by random selection (such as flipping a coin – though now usually done by computer); the patient has an equal chance of being assigned to any of the intervention groups. Randomization eliminates bias in treatment assignment by investigators and produces similar groups of patients in each arm of the study.

Risk Group – A selection of patients with the same type of disease grouped together based on certain clinical and/or biological factors (e.g. age, disease stage, gene abnormalities)

Single-blind – Either the investigator or the patient, but not both, knows which experimental or control treatment the patient is receiving

Standard Treatment – A treatment that has been evaluated thoroughly and is the currently accepted way that patients with a particular disease are treated; used for comparison to a new treatment being evaluated

Statistical Design – The way a study is set up so that the experimental question being asked will be answered by the end of the study; determines such factors as how many and what types of patients will be enrolled in the study

Translational – Research that combines the use of clinical and laboratory studies

Toxicity – Undesirable side effects

Window – Evaluation of a new agent by administering it prior to beginning standard treatment


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