The short answer
A trial tests whether a treatment is safe and works. The NCI says placebos are rarely used in cancer treatment trials and you can leave a study at any time. Costs split into patient care and research categories.
Phase 1 tests safety and dose, phase 2 tests whether it appears to work, phase 3 compares it to standard treatment, and phase 4 looks at long-term safety after FDA approval.
Randomization assigns groups by chance, most often by computer, to prevent bias.
The NCI says placebos are rarely used in cancer treatment trials, and you are told in advance if one is used.
Informed consent is a process you can take home, discuss, and question before signing.
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This page is for people with cancer who are thinking about joining a clinical trial. It explains trial phases, randomization, consent, costs, and questions to ask.
What a Trial Actually Is
A clinical trial is a study that tests whether a treatment is safe and whether it works. Joining one is a real decision with real trade-offs. Ask your care team about trials that may fit your situation, and ask early.
The Phases in Plain Language
Phase 1 asks whether a treatment is safe, what its side effects are, and the highest dose people can tolerate. The NCI says these studies are small, around 15 to 30 people. The main aim is safety, not benefit.
Phase 2 asks whether the treatment appears to work against a specific cancer. The NCI says these enroll 50 to 100 people.
Phase 3 compares the new approach against the current standard treatment. The NCI says these studies enroll from 100 to several thousand people. This is the phase that changes practice, and it is where randomization comes in.
Phase 4 happens after FDA approval. It looks at long-term safety and effectiveness.
Randomization and the Placebo Question
Randomization means a computer, not your doctor, assigns which group you join. The NCI says a computer is most often used to assign people to groups, which prevents bias.
Many people worry they will be given a sugar pill instead of treatment. The NCI says placebos are rarely used in cancer treatment clinical trials. If a placebo is used, you are told in advance and can ask questions before you decide.
Ask directly what you would receive in each group, and whether anyone receives nothing.
Informed Consent Is a Process
The NCI says the team explains the trial's purpose, procedures, risks and benefits, and gives you written information. A consent document typically covers:
- the purpose of the study
- what will happen
- known and possible risks
- likely benefits
The NCI describes informed consent as a process in which the research team explains the trial to you before you decide. Ask the team to explain anything that is unclear. Signing does not take away your right to leave.
The NCI says you can leave a study at any time and can always ask questions. Researchers also submit each study plan for review by an institutional review board (IRB), an independent group that reviews it.
The Money Questions People Forget to Ask
Costs generally split into two categories. The NCI lists patient care costs, such as doctor visits, hospital stays, lab tests and imaging, as often covered by insurance. Research costs, such as study drugs and research-only tests, may not be covered by insurance. Many trial costs are covered by the study sponsor, an insurance plan, or sometimes you.
The NCI says Medicare and Medicaid cover routine patient care costs in clinical trials. TRICARE covers medical costs in NCI-sponsored trials for people with DOD coverage, and eligible veterans can take part at VA medical centers. Before enrolling, ask the study coordinator which costs are covered. If coverage is denied, the NCI suggests contacting your plan's billing office to appeal.
Ask what the trial pays for, what you will be billed for, and how many extra visits are involved. The NCI says travel costs such as lodging, meals and childcare may get financial support, so ask the research team.
Questions Worth Writing Down
- Why is this trial being done?
- What is the alternative if I do not join?
- How many extra appointments and tests are involved?
- What are the known side effects?
- Who do I call at three in the morning?
- What happens if the treatment works and the trial ends?
Sources
Common questions
Will I get a placebo instead of treatment?
The NCI says placebos are rarely used in cancer treatment clinical trials. If a placebo is used, you are told in advance and can ask questions before you enroll. Ask the team what each group receives.
Are trials only for people who have run out of options?
Not necessarily. The NCI lists several kinds of trials, including treatment, prevention, screening and supportive care trials. Ask your care team about trials that may fit your situation.
Can I change my mind after signing?
Yes. The NCI says you can leave a study at any time. Tell the team if you decide to leave, and ask what follow-up they advise.
Who pays for a clinical trial?
Costs generally split in two. The NCI says patient care costs, such as doctor visits, hospital stays, lab tests and imaging, are often covered by insurance. Research costs, such as study drugs and research-only tests, may not be. Medicare and Medicaid cover routine patient care costs in clinical trials. Ask the study coordinator which costs are covered before you enroll.
Is a trial riskier than standard treatment?
There is uncertainty, and side effects may not all be known. The NCI says phase 1 studies look at safety, side effects and tolerable dose. Each study plan is submitted for institutional review board (IRB) review. Ask the team about the known risks of the trial you are considering.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-10-02 what this meansLast updated: 2026-08-10Next planned review: 2027-01-30
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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