Clinical trials of cancer treatments

Clinical trials of cancer treatments: what to know

Clinical trials are research studies that look for better ways to prevent, find, and treat cancer. People volunteer to take part. Trials help doctors learn what works, what does not, and how to make care safer and more effective.

This guide explains how trials work, the possible benefits and downsides, and questions to discuss with your oncology team.

What is a clinical trial?

A clinical trial tests ideas to improve health. In cancer, trials can:

• Test new treatments to see if they work better than current care
• Test ways to prevent cancer or lower risk
• Test new tools to find or diagnose cancer earlier

Most treatment trials compare a new therapy with the usual treatment or with a placebo. A placebo looks like a medicine but has no active drug. Not all trials use placebos. In cancer, placebos are rarely used alone when an effective standard treatment exists; they may be used along with standard care.

How do comparisons and assignment work?

• Randomization: In many trials, a computer assigns you to a study group. This helps make fair comparisons.
• Blinding: Sometimes you, your care team, or both do not know which treatment you get during the study. This helps reduce bias.
• Group sizes: It is not always 50/50. Some trials use different ratios (for example, 2:1).

Types (phases) of treatment trials

• Phase I (1): Checks safety, best dose, how often to give it, and early side effects.
• Phase II (2): Gives the new treatment to people with a specific cancer to see how well it works and to watch side effects.
• Phase III (3): Compares the new treatment with the usual treatment or with a placebo to learn if it is better, the same, or worse, and how side effects compare.

Who can join a clinical trial?

It depends on the study. Each trial has rules called eligibility criteria. These may include:

• Your cancer type, stage, or biomarker (for example, a gene change)
• Previous treatments you have had
• Age, overall health, and other medical conditions
• Lab results or imaging findings

Some trials enroll only people with cancer (common in phases II and III). Others may include healthy volunteers. You may need to answer questions, have a physical exam, and do tests to see if you qualify. Your oncology team can help you check.

Possible benefits

• Access to a new treatment before it is widely available
• Close monitoring by a team experienced with your type of cancer
• More information about your health through study tests
• Helping future patients by contributing to research

Healthy volunteers can also help others and learn about research and their health.

Possible downsides and uncertainties

• Side effects may be unknown or stronger than expected
• The new treatment might not work better than current care, or may not work for you
• You may not receive the new treatment if you are assigned to the comparison group
• More visits, tests, or time at the clinic than usual
• Travel, time away from work or school, and logistics can be challenging
• Insurance may be billed for routine care; coverage varies by plan and state

Your rights and safety

• Informed consent: A study team member explains the purpose, schedule, risks, and alternatives. You can ask questions. If you agree, you sign a consent form.
• Voluntary participation: It is your choice to join. You can leave the trial at any time, for any reason.
• Oversight: Independent groups (an Institutional Review Board and sometimes a Data and Safety Monitoring Board) review trials before they start and while they run to help protect participants.
• Stopping rules: Trials can be paused or stopped early if there are safety concerns or if a treatment clearly works better.

Costs, coverage, and support

Most sponsors provide the study drug and extra research tests needed only for the study. Usual care costs (like routine labs or scans) are often billed to insurance. Coverage depends on your plan and location.

• Ask to speak with a financial counselor about expected costs.
• Ask about help for travel, lodging, meals, or parking. Some studies or nonprofits offer support.
• Keep receipts if you are told expenses may be reimbursed.

What to expect if you take part

• Screening: Tests to confirm you qualify.
• Study visits: A schedule of visits, treatments, and tests (sometimes called a calendar).
• Daily life: You may be asked to keep a diary, use an app, or track symptoms.
• Communication: Tell your team about all medicines, vitamins, or supplements you use. Do not start or stop anything without discussing it with your oncology team.
• Follow-up: Some trials include check-ins after treatment ends to track long-term effects.

Questions to ask your oncology team

• What is the goal of this trial for my type of cancer?
• How does this treatment work? Has it been tested before?
• What are the possible benefits and risks for me?
• What are my other options, including standard treatments?
• How are people assigned to study groups? Is a placebo used?
• How often are visits and tests? How long does the trial last?
• What costs are covered? What might I pay?
• If I have side effects, how will they be managed?
• If I leave the study, what happens next?

Finding cancer clinical trials

• National Cancer Institute (NCI): About Clinical Trials
• NCI: Search for Cancer Clinical Trials
• ClinicalTrials.gov (U.S. and international studies)
• ASCO Cancer.Net: Clinical Trials
• Ask your oncology clinic or nearby academic cancer center about open studies

Joining a clinical trial is a personal choice. Learning the facts and talking openly with your oncology team can help you decide what is right for you.

Last reviewed: 2025-12-04