Clinical trials glossary: 12 terms to know

New and better cancer treatments are discovered through clinical trials. By joining one, patients get access to the most cutting-edge treatments.

If you’re considering enrolling in a clinical trial, or if you’re trying to understand the results from one, you may be wondering what words, like Phase, mean. We spoke with Funda Meric-Bernstam, M.D., to learn what you should know to understand clinical trials.

What are clinical trial phases?

Clinical trials happen in four different phases:

• Phase I trials are the first time a drug is being used in humans. They may also explore different dosing schedules or new drug combinations. These trials are looking to determine a safe dosage of the drug, possible side effects and early signs of how well the therapy works. In the initial phase, a clinical trial enrolls about 20 to 50 patients. After a drug dose and schedule is determined, trials may also have expansion cohorts to treat additional patients with specific tumor types.
• Phase II clinical trials include about 20 to 100 patients. They’re studying if a treatment works in treating a specific type of cancer.
• Phase III clinical trials enroll hundreds of patients. They compare the experimental approach with the standard treatment approach to see if the new approach is better.
• Phase IV trials are looking at the long-term benefit of the new drugs as well as any lingering side effects.

Regardless of which Phase you’re considering joining, Meric-Bernstam says there are other terms used to discuss clinical trials. Here’s a glossary of more clinical trial terms you may need to know.

Adverse event – When an enrolled patient experiences a negative change in health, it’s known as an adverse event. It’s important to note that this change may or not be caused by the experimental treatment. Adverse events can be mild, such as skin irritation or fatigue, or they can be more severe, such developing diabetes.

Arm – To determine if a new treatment is more effective than current treatments, Phase II and Phase III clinical trials divide enrolled patients into different groups – called arms – for easy comparison.

Basket trial – Also sometimes called a bucket trial, these clinical trials test a treatment in patients who have different types of cancer but have a common genetic mutation or biomarker that’s determined through genomic profiling.

Eligibility criteria – To create the best conditions for an accurate and unbiased study, clinical trials have guidelines on which patients can and cannot enroll. The purpose of eligibility criteria is to remove the opportunity of chance, which could alter the study’s results. The criteria are different for each study, but they can include age, diagnosis and medical history.

Endpoint – An endpoint is a result of a clinical trial that can be evaluated objectively to show there’s benefit in the experimental treatment. There can be several endpoints in a study. One example is the trial’s response rate, which is the percentage of patients whose tumor shrank or disappeared because of the experimental therapy. Another endpoint is the overall survival rate, which is the percentage of patients who are still alive at a specific time, often five years out from treatment.

Genomic profiling – The goal of genomic profiling is to identify molecular characteristics of a tumor that are driving its growth that can potentially be targeted for treatment with targeted therapies or immunotherapy. Although not every tumor has a known genetic target, Phase I clinical trials are offering some patients this new option.

Performance status – In order to safely participate in a clinical trial, patients need to be healthy enough for everyday activities, such as walking, bathing and getting dressed. You’ll be evaluated on your ability to complete these tasks without someone’s help. This score is known as your performance status.

Placebo – A placebo is a substance that seems like a drug but has no medical benefit. Although they’re sometimes called sugar pills, placebos aren’t always in a pill form. Sometimes used in later-phase clinical trials, a placebo is most commonly combined with the standard treatment, known as the control arm. In the experimental arm, patients may receive an experimental treatment or the standard treatment plus the experimental drug.

Randomization/randomized –The process of randomly assigning patients to different arms of treatment is called randomization. This removes the opportunity for bias or chance. A randomized clinical trial can be blind, which is when patients don’t know to which arm they’ve been assigned, or trials can be double-blind, which is when neither the patients nor the doctors know.

Research biopsy – A biopsy is when a sample of tissue is removed from a tumor for testing. They help with initial diagnosis, but some clinical trials have additional biopsies that are done throughout treatment to better understand how the experimental drug works.

Umbrella trial – The opposite of a basket trial, these trials study patients who have the same type of cancer but with different gene mutations or biomarkers. They’re offered different treatments based on their tumors’ molecular characteristics.

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