Understanding Clinical Trials
Your guide to cancer research studies and how to participate
Quick Facts About Clinical Trials
- Clinical trials test new ways to prevent, detect, or treat cancer
- All current standard treatments were once tested in clinical trials
- Participation is always voluntary and you can leave at any time
- Trials follow strict scientific and ethical guidelines
- Sponsors often pay for the study drug, and health plans generally cover routine care
- About 7% of adults with cancer joined a treatment trial in a large US study, and about 1 in 5 took part in some form of cancer research
What Are Clinical Trials?
Clinical trials are research studies that test new ways to prevent, detect, diagnose, or treat diseases like cancer. They are essential for advancing medical knowledge and improving patient care.
Types of Cancer Clinical Trials
- Treatment Trials: Test new treatments or new ways to use existing treatments
- Prevention Trials: Test ways to prevent cancer in people who haven't had it or prevent recurrence
- Screening Trials: Test new ways to detect cancer early
- Diagnostic Trials: Test new procedures for diagnosing cancer
- Quality of Life Trials: Explore ways to improve comfort and quality of life
- Biomarker/Genetic Trials: Study genetic factors and molecular markers
Who Conducts Clinical Trials?
- National Cancer Institute (NCI)
- Pharmaceutical and biotechnology companies
- Academic medical centers and universities
- Cooperative research groups (SWOG, ECOG-ACRIN, etc.)
- Community hospitals and cancer centers
Clinical Trial Phases
Clinical trials are conducted in phases, each designed to answer specific research questions:
Phase 0
Purpose: Exploratory studies
Participants: Usually 10-15 people
Focus: How the body processes the drug
Duration: Short, often about a week or less
Very small doses to study drug behavior, not treatment effect
Phase I
Purpose: Safety and dosage
Participants: About 15-30 people
Focus: Safe dose range, side effects
Often the first studies in humans, with doses raised step by step between groups
Phase II
Purpose: Efficacy and safety
Participants: About 50-100 people
Focus: Does it work? Further safety evaluation
Tests effectiveness in specific cancer types, such as whether tumors shrink or growth slows
Phase III
Purpose: Compare to standard treatment
Participants: About 100 to several thousand people
Focus: Is it better than current treatment?
Randomized controlled trials, FDA approval basis
Phase IV
Purpose: Post-market surveillance
Participants: Large, diverse groups
Focus: Long-term effects, optimal use
Duration: Ongoing
After FDA approval, monitors real-world use
Participant numbers are typical figures and vary from trial to trial.
What the Phases Mean for You
- Phase 0: The dose is too small to treat the cancer. These studies are not meant to help the people who take part, so ask what you would gain and what it could delay
- Phase I: The main question is safety and dose. The treatment has been tested in few people, so unknown risks are higher. Some people do benefit, but that is not the study's main goal
- Phase II: The study asks whether the treatment works against a given cancer. Most people get the study treatment, though some phase II trials compare groups
- Phase III: You are assigned by chance to the new treatment or the current standard. Neither you nor your doctor picks your group
A phase number is not a grade. A phase I trial is not worse than a phase III trial. The phase tells you what question the study is asking and how much is known so far.
Finding Clinical Trials
Clinical Trial Search Resources
ClinicalTrials.gov
NIH database of all registered U.S. and international trials
Website: clinicaltrials.gov
NCI Clinical Trials Search
National Cancer Institute's trial database
Website: Find NCI-supported clinical trials
Phone: 1-800-4-CANCER (1-800-422-6237), Monday to Friday, 9:00 a.m. to 9:00 p.m. Eastern
Drug Company Trials
Check pharmaceutical company websites for sponsored trials
Cancer Centers
NCI-designated cancer centers often have many trials
Search Tips
Trial registries are searched by a handful of fields. Having these ready before you start makes the results far more usable:
- Exact diagnosis: Search the specific histology from your pathology report ("triple-negative breast cancer", "clear cell renal carcinoma"), not just the organ. Broad terms return hundreds of irrelevant trials.
- Stage and prior treatment: Most trials specify a line of therapy — first-line, second-line, or relapsed/refractory. Knowing how many regimens you have already had rules trials in or out quickly. See our cancer staging guide if you are unsure how your stage is written.
- Biomarkers: Note any results such as HER2, EGFR, ALK, PD-L1, BRCA, or MSI status. A growing share of trials enrol by biomarker rather than by cancer type.
- Distance you can travel: Filter by state or ZIP first, then widen. Some trials reimburse travel; ask the study coordinator.
- Recruitment status: Limit to "Recruiting" or "Not yet recruiting" — completed trials still appear in search results.
Search the full registry at ClinicalTrials.gov, or call the NCI Cancer Information Service at 1-800-4-CANCER for help narrowing a search. Bring the NCT number of any trial you find to your oncologist — they can confirm eligibility far faster than the registry listing can.
A Step-by-Step Search
- Ask your oncologist first. Ask whether a trial fits you now, and whether one might fit later. Some trials require that you have not had certain treatments, so it helps to ask before you start a new one.
- Gather your records. Have your pathology report, stage, list of past treatments with dates, and biomarker results ready.
- Run a basic search. On the NCI site, enter your cancer type, age, and ZIP code. This searches within 100 miles.
- Narrow it down. The advanced search can filter by subtype, stage, drug, prior treatment, phase, and hospital. You can also widen the distance up to 500 miles. Each added filter gives fewer results, so skip any that do not apply.
- Read each listing. Check the purpose, the phase, the eligibility rules, and the trial locations.
- Contact the study team. Each listing gives a contact. Ask whether the trial is still enrolling and whether you may qualify.
Prefer not to search alone? Cancer Information Service specialists can run a search with you by phone or by LiveHelp chat, at no cost. The American Cancer Society also offers a trial matching service called ACS ACTS.
Eligibility & Enrollment
Common Eligibility Criteria
Inclusion Criteria (Must Have)
Exclusion Criteria (Must Not Have)
Important Notes:
- Each trial has specific eligibility criteria
- Criteria ensure participant safety and valid results
- Not meeting criteria for one trial doesn't exclude you from others
- Your oncologist can help identify suitable trials
Why Trials Have Rules About Who Can Join
Eligibility rules do two jobs. They help keep people safe by leaving out those more likely to be harmed. They also help make the results clear, because the group being studied is similar enough to compare.
Inclusion criteria are what you must have to join. Exclusion criteria are what would keep you out. Two terms in the checklist above may need explaining:
- Performance status: How well you can manage daily activities
- Organ function: Often checked with blood tests of your blood counts, kidneys, and liver
Screening tests come after you ask to join. You may need new blood work, scans, or a biopsy, and a listing alone cannot confirm you qualify. If you are turned down, ask why. A value may change, or another trial may fit better.
The Clinical Trial Process
Finding and Referral
- Identify potential trials through searches or physician referral
- Initial contact with trial coordinator
- Preliminary eligibility screening
Screening Visit
- Detailed eligibility assessment
- Medical history review
- Physical examination
- Required tests (blood work, scans, etc.)
Informed Consent
- Full explanation of the trial
- Review of risks and benefits
- Time to ask questions
- Voluntary signing of consent form
- Right to withdraw at any time
Randomization (if applicable)
- Random assignment to treatment group
- May be blinded (you don't know which treatment)
- Ensures unbiased results
Treatment Phase
- Receive assigned treatment
- Regular monitoring visits
- Side effect reporting
- Required tests and procedures
Follow-up
- Continue monitoring after treatment
- Long-term outcome tracking
- Safety surveillance
- May continue for years
Informed Consent
Informed consent is the process of learning about a trial before you decide. It is more than a signature. The research team explains the study, and you can ask questions at any point, including after you join.
What the Team Should Explain
- Why the study is being done
- What treatments, tests, and visits it involves
- The possible risks and benefits
- Your other options, including treatment outside the trial
- Your rights, including your right to leave
- How your medical records will be kept private
The consent form puts this in writing. You have the right to receive it in a language you understand. If you sign, you should get a copy to keep.
Before You Sign
- Take the form home if you can, and read it with someone you trust
- Write down your questions, and ask about any word you do not know
- Ask what happens to your care if you say no. You should still receive care
- Ask who to call with questions about your rights
Signing does not lock you in. You can leave at any time, and you will be told about new information as it becomes available. If you leave, talk with your doctor so you can stop safely and plan what comes next.
Costs and Insurance
Joining a trial can change what you pay. Costs usually fall into three groups:
- Routine care costs: Things you would need even outside a trial, such as doctor visits, hospital stays, standard treatment, lab tests, and imaging. Health plans usually cover these. Your plan may require approval first
- Research costs: The study drug, tests done only for the study, and extra visits. Insurance often does not cover these, but the sponsor often pays them
- Travel and other costs: Lodging, meals, parking, and child or elder care. Some studies help with these. Ask the research team
Who Covers What
- Private insurance: The Affordable Care Act requires insurers to cover routine patient care costs for people in approved trials. Insurers cannot drop or limit coverage because you join one. They generally do not have to pay for the treatment being studied or for data collection
- Medicaid: Covers routine patient care costs in a trial. Eligibility rules vary by state
- Medicare: Will likely cover many routine costs for approved trials. Ask what applies to your trial
- TRICARE: Can reimburse medical costs for NCI-sponsored cancer prevention and treatment trials
- Veterans Affairs: Eligible veterans can join NCI-sponsored trials at VA medical centers
Before You Enroll
- Ask the study coordinator for a list of covered and non-covered costs
- Call your insurer. Claims are often reviewed case by case
- Check that your main cancer doctors and the trial site are in network
- Ask a hospital financial counselor to review your likely bills
- If insurance refuses something, ask whether the sponsor can help
Benefits and Risks
✅ Potential Benefits
- Access to new treatments before widely available
- Close monitoring by research team
- Contribute to medical knowledge
- May receive effective treatment
- Often no cost for trial treatment
- Additional medical attention
- Help future patients
⚠️ Potential Risks
- Unknown side effects
- Treatment may not be effective
- More time commitment
- Additional tests and procedures
- May receive placebo (in some trials)
- Travel to trial site
- Insurance may not cover all costs
Your Rights as a Participant
- Participation is always voluntary
- You can leave the trial at any time
- Leaving won't affect your standard care
- Your privacy is protected by law
- You'll be informed of new risks or findings
- You can ask questions at any time
Questions to Ask
Important Questions for Your Trial Team
About the Trial
- What is the purpose of this trial?
- What phase is this trial?
- How long will the trial last?
- Has this treatment been tested before?
- What were the results of previous studies?
About Treatment
- What treatments will I receive?
- How is it given (IV, pills, etc.)?
- How often will I receive treatment?
- Will I know which treatment I'm getting?
- Can I continue my current medications?
About Risks and Benefits
- What are the possible side effects?
- How do risks compare to standard treatment?
- What happens if the treatment doesn't work?
- What are the alternatives to this trial?
Practical Matters
- How many visits are required?
- Will I need to stay in the hospital?
- Who pays for the treatment?
- Will insurance cover trial-related costs?
- Is travel assistance available?
- Who do I contact with problems?
Myths and Facts About Clinical Trials
Myth: Clinical trials are a last resort when nothing else works.
Fact: Trials are available for all stages of cancer, including newly diagnosed patients. Some test new treatments, and others test new ways to use existing ones.
Myth: I might get a placebo instead of real treatment.
Fact: Placebos are rarely used in cancer treatment trials. Most compare a new treatment to standard care. A placebo may be used when no standard treatment exists, or added to standard treatment. You'll be told ahead of time.
Myth: I'll be treated like a guinea pig.
Fact: Trials follow strict ethical guidelines. Your safety is the top priority, with close monitoring and the right to leave anytime.
Myth: Clinical trials are too risky.
Fact: All trials carry risks, especially early-phase trials, and a new treatment may not help you. Trials also have safety measures, ethics review, and informed consent.
Myth: My insurance won't cover it.
Fact: The Affordable Care Act requires insurers to cover routine costs in approved trials. The trial sponsor usually covers the investigational treatment.
Frequently Asked Questions
Who pays for a cancer clinical trial?
Usually two groups share the cost. Your health plan is generally asked to pay routine care costs, such as doctor visits and standard tests. The study sponsor often pays for the study drug and tests done only for research. Ask the study team for a written list of what you may have to pay.
Will I get a placebo instead of treatment?
This is uncommon. The National Cancer Institute says placebos are rarely used in cancer treatment trials. When one is used, it is usually added to standard treatment or used when no standard treatment exists. You will be told before you agree to join, and the consent form will explain it.
Can I leave a clinical trial after I sign the consent form?
Yes. You can leave at any time and for any reason, even after you sign. It is a good idea to talk with your doctor first, so that you can stop safely and plan your next treatment.
How do I find a clinical trial for my cancer?
Start by asking your oncologist. You can also search the National Cancer Institute trial finder or ClinicalTrials.gov, or call the NCI Cancer Information Service at 1-800-4-CANCER for free help. Have your exact diagnosis, stage, past treatments, and biomarker results ready.
What is the difference between phase 1, 2 and 3 trials?
Phase 1 trials look for a safe dose and side effects in a small group. Phase 2 trials check whether the treatment works against a certain cancer. Phase 3 trials compare the new treatment with the current standard in a larger group, often by random assignment.
Why was I told I am not eligible for a trial?
Each trial has rules about who can join, such as cancer type and stage, past treatment, age, and organ function. These rules protect people and help keep results clear. Not fitting one trial does not rule you out of others, so ask whether another trial might fit.
Additional Resources
Sources
- Phases of Clinical Trials, National Cancer Institute
- Gupta UC, et al. Phase 0 clinical trials in oncology new drug development. Perspect Clin Res. 2011
- Informed Consent, National Cancer Institute
- Placebos in Cancer Clinical Trials, National Cancer Institute
- Who Pays for Clinical Trials?, National Cancer Institute
- Help Finding NCI-Supported Clinical Trials, National Cancer Institute
- What Are Clinical Trials?, National Cancer Institute
- Things to Consider Before Taking Part in a Clinical Trial, American Cancer Society
- Clinical Trials, American Cancer Society
- One in Five People With Cancer Participate in Clinical Research, The ASCO Post, 2024
Important: This information is educational only. Discuss clinical trial participation with your oncologist to determine if it's right for your situation. Always review the specific trial's informed consent document carefully.