Clinical trials explained

What cancer clinical trials are, how the phases work, what randomization and placebos mean, how you are protected, and how to find a trial that might suit you.

6 min read · last reviewed September 30, 2026

You may have heard your team mention a "clinical trial," or wondered whether one might be right for you. The idea can feel a bit scary. Some people imagine being a "guinea pig." In reality, clinical trials are carefully planned and closely watched. They are how cancer care gets better, and many of today's standard treatments were once tested in trials.

This guide explains what trials are, how they work, and how to decide whether one is right for you.

What is a clinical trial?

A clinical trial is a research study with people. Cancer trials test new ways to:

• Treat cancer, such as a new medicine, a new mix of treatments, or a new way of giving radiation or surgery.
• Ease side effects and improve quality of life.
• Find cancer early or prevent it.

Not all trials test new medicines. Some test whether a shorter or gentler treatment works as well as the usual one. Some look at exercise, diet or emotional support.

The phases of a trial

Treatment trials usually go in steps, called phases:

• Phase 1: tests a new treatment in a small group of people for the first time, to find a safe dose and learn about side effects.
• Phase 2: looks at whether the treatment works against a certain cancer, and learns more about side effects.
• Phase 3: compares the new treatment with the current standard treatment (the best treatment already in use) in a larger group, to see which works better.

After a treatment is approved, some studies keep tracking it to learn more about long-term effects.

Randomization and placebos

In many phase 3 trials, people are put into groups by chance, like flipping a coin. This is called randomization. One group gets the new treatment. The other gets the standard treatment. Neither you nor your doctor can choose your group. This makes the results fair.

A placebo is a "dummy" treatment with no active medicine. Many people worry they'll get "nothing." Placebos are rarely used alone in cancer treatment trials. In most trials, everyone gets at least the standard treatment. If a placebo is part of a trial, it's usually given together with standard treatment, and you'll be told about this before you agree.

How you are protected

• Ethics review. Before a trial can start, an independent ethics board reviews it to protect the people taking part.
• Informed consent. The research team will explain the trial's purpose, tests, possible benefits and risks, and your other options. You'll get it in writing. Take your time, take it home, and ask questions.
• You can leave at any time. Signing the consent form doesn't lock you in. If you leave, you'll still get cancer care.
• Close monitoring. People in trials are often checked more closely than usual.

Possible benefits and downsides

Possible benefits:

• You may get a new treatment before it's widely available.
• You'll be closely followed by a care team.
• You help people with cancer in the future.

Possible downsides:

• A new treatment may not work better than standard care, or may have unexpected side effects.
• You may need more visits, tests or travel.
• You may not get the new treatment if you're in the standard group.

There's no right or wrong answer. Some people join trials, and some don't. What matters is that the choice fits you.

Who can join?

Each trial has rules about who can take part. These may include the type and stage of cancer, past treatments, age and general health. These rules keep people safe and make the results clear. If you don't qualify for one trial, you might qualify for another.

Tip: Ask about trials early, before you start treatment if you can. Some trials are only for people who haven't had certain treatments yet.

What about costs?

Costs depend on the trial and where you live. Often the trial pays for the study medicine and extra tests. Your usual care may be covered as normal. Ask the research team:

• What will the trial pay for?
• Will I have extra costs for travel, parking or time off work?
• Is any help with costs available?

How to find a trial

• Ask your cancer team. They know which trials are open at your centre and nearby.
• In Canada, search Cancer Trials Canada (cancertrialscanada.ca), or call the Canadian Cancer Society at 1-888-939-3333.
• In the U.S., search ClinicalTrials.gov, or call the National Cancer Institute at 1-800-4-CANCER (1-800-422-6237).
• Bring what you find to your team. They can help you tell whether a trial fits you.

Something you can do this week: At your next appointment, ask, "Is there a clinical trial that might be right for me?"

Questions to ask about a trial

• What is this trial testing, and why?
• What phase is it?
• What treatment would I get in each group? Could I get a placebo?
• What are the possible benefits and risks for me?
• How many visits, tests and scans are involved? Where?
• What other options do I have if I don't join?
• Will it cost me anything?
• What happens if I want to leave the trial?
• Who do I call with questions or problems, day or night?

This article is general information, not medical advice. Talk with your health care team about your own situation. In an emergency, call 9-1-1 or your local emergency number.

In an emergency, call 9-1-1 or your local emergency number.

General information, not medical advice. It does not replace your own care team. If you think you or someone else is having a medical emergency, call 9-1-1 or your local emergency number. If you are in crisis or thinking about suicide, call or text 9-8-8 (Canada and the US).

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