Clinical Trials Glossary
The words you will hear when learning about clinical trials, defined in plain language. For general cancer terms, see the main Cancer Explained glossary.
Educational only — not medical advice. Cancer Explained does not recommend clinical trials or determine eligibility. Whether a clinical trial is appropriate for you depends on your diagnosis, test results, and treatment history — please discuss clinical trials with your oncology team.
- Adverse Event
- Any unwanted or unexpected medical problem that happens to a person during a trial, whether or not it is caused by the treatment.Source: NCI (External — official resource)
- Biomarker
- Something in the body, blood, or a tumor that can be measured and that gives information about a disease or how a treatment is working.Source: NCI (External — official resource)
- Blinding
- Keeping certain people from knowing which group a participant is in, which helps keep a trial's results fair and unbiased.Source: NCI (External — official resource)
- Clinical Trial
- A research study that tests a new way to prevent, find, or treat disease in people who volunteer to take part.Source: NCI (External — official resource)
- Control Group
- The group in a trial that receives the standard treatment, or sometimes standard care plus a placebo, to compare against a new approach.Source: NCI (External — official resource)
- Data and Safety Monitoring Board
- An independent group of experts that reviews a trial's safety information while the study is going on and can recommend changes.Source: NCI (External — official resource)
- Eligibility Criteria
- The set of rules that decide who can take part in a trial, such as cancer type, stage, past treatments, age, and overall health.Source: NCI (External — official resource)
- Enrollment
- The process of joining a clinical trial after meeting its eligibility criteria and completing informed consent.Source: NCI (External — official resource)
- Informed Consent
- The process of learning the key facts about a trial, including its purpose, benefits, and risks, before choosing whether to take part.Source: NCI (External — official resource)
- Institutional Review Board (IRB)
- A group of doctors, scientists, and community members that reviews a trial to protect the rights and safety of the people who take part.Source: NCI (External — official resource)
- Phase
- One of the steps in testing a treatment. Early phases focus on safety and dose, and later phases test how well a treatment works.Source: NCI (External — official resource)
- Placebo
- An inactive look-alike with no treatment effect. In cancer treatment trials it is rarely used alone, and when used it is usually added to standard care.Source: NCI (External — official resource)
- Primary Endpoint
- The main result a trial is designed to measure, chosen before the study begins to answer its central question.Source: NCI (External — official resource)
- Principal Investigator
- The lead researcher responsible for running a clinical trial and for the safety of the people who take part.Source: NCI (External — official resource)
- Protocol
- The detailed written plan for a trial that describes its purpose, who can join, what will happen, and how people will be kept safe.Source: NCI (External — official resource)
- Randomization
- Assigning people in a trial to different groups by chance, usually by computer, so the comparison between groups stays fair.Source: NCI (External — official resource)
- Secondary Endpoint
- An additional result a trial measures beyond its main question, which can offer more information about a treatment.Source: NCI (External — official resource)
- Standard of Care
- The treatment that experts agree is best for a certain condition right now and that most people would receive.Source: NCI (External — official resource)