The Patient's Guide to Cancer Clinical Trials
Written by: North Editorial Staff, reviewed by Laura Morrissey, RN, BSN · Last reviewed: February 2026 · Next review due: February 2027
Key Takeaways
Cancer clinical trials are the process through which every available cancer treatment was proven safe and effective — and they may give you access to new therapies not yet available through standard care.
Trials progress through four phases: Phase 1 (safety, 20–100 participants), Phase 2 (effectiveness, 100–500), Phase 3 (comparison to standard care, 1,000–3,000+), and Phase 4 (post-approval monitoring).
You will almost never receive a placebo instead of real treatment. When placebos are used in cancer trials, they are given alongside standard care, not in place of it.
Multiple layers of safety protections — including IRBs, Data Safety Monitoring Boards, and your dedicated research team — monitor your health throughout the trial.
You can find trials through your oncologist, ClinicalTrials.gov, the NCI Cancer Information Service (1-800-422-6237), or a trial matching service like North.
What Are Cancer Clinical Trials?
Cancer clinical trials are carefully designed research studies that test new ways to prevent, detect, or treat cancer. They are the process through which every cancer treatment available today — from chemotherapy to immunotherapy to targeted therapy — was proven safe and effective before becoming part of standard care.
According to the National Cancer Institute, clinical trials are the final step in a long process of research that begins in the laboratory and are essential for developing new cancer therapies. Without clinical trials, there would be no way to know whether a promising treatment discovered in a lab actually works in real patients with real cancers.
Trials may study new drugs, new combinations of existing treatments, new surgical techniques, new radiation approaches, or entirely new categories of therapy like CAR-T cell treatment. Some trials focus on prevention or early detection rather than treatment. According to the American Cancer Society, the main types of cancer clinical trials include treatment trials, prevention trials, screening trials, and supportive care trials — each serving a different purpose in advancing cancer research.
Every clinical trial follows a detailed plan called a protocol. The protocol outlines what the study will do, how it will be conducted, why each step is necessary, and who can participate. Protocols are reviewed and approved by independent ethics boards called institutional review boards (IRBs) before any patient is enrolled.
Clinical trials are conducted at cancer centers, hospitals, and clinics across the country. Some trials now offer remote or decentralized participation, meaning that certain visits, tests, or check-ins can happen closer to home or through telehealth.
For many patients — especially those with advanced or metastatic cancer or cancer that hasn't responded to standard treatment — clinical trials represent access to therapies that aren't available any other way. The growth of precision medicine — using biomarkers and genetic testing to match patients with treatments tailored to their tumor's characteristics — has made clinical trials more important than ever.
How Clinical Trial Phases Work
Cancer clinical trials progress through a series of phases, each designed to answer different questions about a treatment's safety, effectiveness, and optimal use. Not every treatment makes it through all phases — and that's by design. The system filters out treatments that aren't safe or effective enough before they reach widespread use.
Phase 1: Safety and Dosing
Phase 1 trials are the first time a new treatment is tested in humans. Their primary purpose is to determine whether the treatment is safe, identify its side effects, and find the right dosage. These trials typically enroll 20 to 100 participants, often people whose cancer has not responded to standard treatments. According to the FDA, approximately 70% of treatments that enter Phase 1 testing move on to Phase 2.
Phase 2: Effectiveness
Phase 2 trials evaluate whether the treatment actually works against a specific type of cancer. Having established a safe dosage range in Phase 1, researchers now focus on whether the drug produces the desired effect — such as shrinking tumors or slowing disease progression. These trials typically enroll 100 to 500 participants who all have the same type of cancer. According to the National Cancer Institute, only about one-third of treatments successfully pass through Phase 2.
Phase 3: Comparison to Standard Care
Phase 3 trials are the large-scale studies that determine whether a new treatment is better than, or at least as good as, the current standard of care. These trials typically enroll 1,000 to 3,000 or more participants across multiple hospitals and are usually randomized, meaning participants are assigned by chance to receive either the new treatment or the standard treatment. Many Phase 3 trials are also double-blind, meaning neither the participants nor the doctors know who is receiving which treatment. Randomization and blinding are critical design elements that ensure results are reliable and free from bias. Successfully completing Phase 3 is what allows a drug company to submit a New Drug Application to the FDA.
Clinical Trial Phase | Percent that Advance to Next Phase | Notes / Source |
Phase I → Phase II | ~70 % | According to FDA general trial transition rates (Phase 1 studies) (U.S. Food and Drug Administration) |
Phase II → Phase III | ~33 % | Roughly one-third advance based on FDA clinical research overview (U.S. Food and Drug Administration) |
Phase III → Approval | ~25 – 30 % | Less than one-third successfully complete Phase III and move toward approval (U.S. Food and Drug Administration) |
Phase 4: Post-Approval Monitoring
Phase 4 trials take place after a treatment has already been approved by the FDA and is available to the public. Their purpose is to monitor the drug's long-term safety and effectiveness in a broader, more diverse population. According to a study published in the Open Med Journal, Phase 4 surveillance has revealed that approximately 4% of approved drugs are eventually withdrawn for safety reasons, underscoring why this ongoing monitoring matters.
The phase a trial is in tells you something important about what's known about the treatment and what questions are still being answered.
Will I Get a Placebo?
Many patients worry that entering a trial means they might get a sugar pill while their cancer goes untreated. This fear is understandable, but it doesn't reflect how cancer trials actually work. According to FDA guidance on cancer trial design, placebo-controlled designs are only appropriate in selected circumstances — when the current standard of care is observation alone (such as in some surveillance situations) or when the trial uses an "add-on" design where all participants receive standard treatment and the experimental group receives the study drug in addition to standard care.
In other words, when placebos are used in cancer trials, they're almost always given alongside active treatment — not in place of it. Ethics rules, overseen by institutional review boards and federal regulators, require that no participant is denied effective, available care.
If a trial you're considering does involve a placebo component, ask the research team to explain exactly how it works. Questions like "Will every participant receive some form of active treatment?" and "What is the standard of care that all groups will receive?" can help you understand the design and make a confident decision.
Is It Safe? Understanding Risks and Protections
Clinical trials involve some degree of uncertainty — that's inherent in testing something new. But multiple layers of protection exist to manage risk and keep participants safe.
Before a new therapy is tested with humans, it must first show promising safety and effectiveness in laboratory and preclinical studies and receive regulatory approval to move forward. According to the FDA, the drug development process from laboratory discovery to approval takes an average of 8 to 15 years.
Once a trial is underway, your safety is monitored at multiple levels. Your research team tracks your health through regular visits, lab work, and imaging. An independent Data Safety Monitoring Board (DSMB) periodically reviews safety data across all participants and has the authority to modify or stop the trial if concerns emerge. And the IRB that approved the trial continues to oversee it throughout.
Every trial carries potential risks, including side effects that may be unknown at the start of the study. These risks are explained to you during informed consent, and you'll be closely monitored for any adverse events throughout your participation. If a side effect occurs, the research team has protocols for managing it — including adjusting your dose, pausing treatment, or stopping the trial treatment if necessary.
The close monitoring that comes with trial participation is itself a form of protection. Many patients in trials receive more frequent and more detailed medical attention than they would on standard treatment. According to a study published in the Journal of Clinical Oncology, participation rates in cancer clinical research have been increasing, in part because patients and clinicians recognize the quality of care that trial participation provides.
Who Is Eligible for a Cancer Clinical Trial?
Each trial has specific eligibility criteria — called inclusion/exclusion criteria — that determine who can participate. These criteria exist to protect patients and to ensure the study can safely and accurately answer its research questions. They are not designed to exclude people arbitrarily.
Inclusion criteria specify who the trial is designed for. This typically includes a specific cancer type and stage, previous treatments received, age range, overall health status (including adequate organ function), and sometimes specific biomarkers or genetic characteristics of the tumor.
Exclusion criteria identify who should not participate, often for safety reasons. These might include certain other medical conditions, medications that could interfere with the study, or recent treatments that could affect results.
According to the National Cancer Institute, eligibility requirements help researchers make sure that participants are similar enough that differences in outcomes can be attributed to the treatment being studied rather than to differences among patients.
Eligibility criteria vary widely across trials. If you don't qualify for one trial, there may be others studying the same treatment or approach with different requirements. According to ClinicalTrials.gov, there are tens of thousands of cancer-related studies actively recruiting participants across the United States and around the world. This is one area where working with your oncologist or a trial matching service can help — they can quickly identify which trials are the best fit for your specific situation.
How to Find a Cancer Clinical Trial
Finding the right clinical trial can feel overwhelming, but there are clear steps you can take and trusted resources to guide you.
Talk to your oncologist. They know your cancer, your treatment history, and your health. Ask directly: "Are there any clinical trials I should consider?" According to data from the National Institutes of Health, healthcare providers are the most trusted source of clinical trial information for the majority of Americans — and asking is often the single most important step.
Search trial databases. ClinicalTrials.gov is the largest clinical trials database in the world, maintained by the U.S. National Library of Medicine. The National Cancer Institute also maintains a cancer-specific search tool at cancer.gov. Both allow you to filter by cancer type, location, phase, and other criteria.
Check your cancer center. Major cancer centers list their currently enrolling trials on their websites. If you're being treated at or near one, their research office can help identify relevant options.
Use a trial matching service. Services like North use your specific diagnosis details — cancer type, stage, biomarkers, treatment history, and location — to search across thousands of trials and deliver personalized matches.
Contact the NCI Cancer Information Service. The National Cancer Institute offers free, personalized assistance to patients looking for clinical trials. You can reach a cancer information specialist by calling 1-800-4-CANCER (1-800-422-6237). According to the NCI, these specialists use the Institute's database to identify trials currently accepting patients.
You don't need to wait for your doctor to suggest a trial. Being proactive about your search is common and encouraged.
What to Expect During a Trial
Participating in a clinical trial may involve regular visits to the trial site for treatment, monitoring, and tests. The frequency depends on the trial — some require weekly visits early on, or follow a monthly schedule, while others are conducted through telemedicine or collect data remotely.
Your Research Team
You'll have a dedicated research team, including a research nurse or study coordinator who serves as your primary point of contact for questions and concerns. This team monitors your health closely throughout the trial through lab work, imaging, physical exams, and your own reports about how you're feeling. The level of attention and monitoring is often more intensive than standard care.
Costs and Coverage
The study treatment itself and research-specific tests are typically covered by the trial sponsor at no cost to you. Routine care costs — doctor visits, standard imaging, lab work — are usually billed to your insurance, just as they would be with standard treatment. Federal law requires most insurance plans to cover routine patient care costs during qualifying clinical trials. Many trials also offer travel reimbursement or stipends. For a detailed breakdown of how insurance works during a trial, see our guide to clinical trial insurance.
Compensation
Unlike some clinical trials that recruit healthy volunteers, such as early vaccine or prevention studies, oncology clinical trials are less likely to offer payment simply for participation. Instead, compensation in cancer trials is most often structured as reimbursement for travel, lodging, parking, or other out-of-pocket expenses. In some cases, participants may also receive a modest stipend to offset the time and inconvenience of additional visits or procedures required by the study. The amount and structure of any compensation are reviewed by institutional review boards to ensure they are appropriate and not coercive. All reimbursement or payment details are clearly outlined in the informed consent document before enrollment.
Ongoing Communication
You'll stay in regular contact with your research team, and you can call between visits if anything comes up. If the treatment is effective, your doctor may be able to continue prescribing it through an extended access program or because the drug has since been approved. If the treatment doesn't work as hoped, your medical team will help you transition to the next best option for your care.
To learn more about practical and emotional resources available during participation, see our guide to patient support during cancer clinical trials.
Your Rights as a Participant
Clinical trial participation is always voluntary, and your rights are legally protected throughout the process.
You have the right to be fully informed about the study before you agree to participate. You have the right to ask questions at any point and receive honest, complete answers. You have the right to know about any new information that emerges during the trial that might affect your willingness to continue. You have the right to leave the trial at any time, for any reason, without it affecting your access to other medical care. And your personal health information is kept confidential under federal privacy regulations.
These rights are overseen by institutional review boards (IRBs) — independent committees that review and approve every trial before it begins and continue to monitor it throughout.
Informed consent is not a contract. It's an ongoing process — a conversation between you and your research team that continues for the duration of the study. You can change your mind at any point, and your decision will be respected.
Questions to Ask Your Oncologist
If you're considering a clinical trial, these questions can help guide the conversation with your care team:
What clinical trials are available for my specific type and stage of cancer?
What is the goal of this trial — is it testing a new treatment, a new combination, or a new approach?
What phase is the trial in, and what does that mean for me?
What are the possible risks and side effects?
How does this trial compare to my current treatment options?
How often would I need to visit the trial site, and where is it located?
Will my insurance cover the costs that the trial doesn't?
What happens if the treatment doesn't work or I want to stop?
Has my tumor been tested for biomarkers that might qualify me for a specific trial?
Can you help me contact the trial's research team?
You don't need to have all the answers before starting the conversation. The goal is to understand your options so you can make the decision that's right for you.
Frequently Asked Questions
Are clinical trials only for people with advanced cancer?
No. Clinical trials exist for every type and stage of cancer, including early-stage cancers and even cancer prevention. Some trials study treatments for newly diagnosed patients, while others focus on patients who have tried previous treatments. The perception that trials are a "last resort" is outdated — many oncologists recommend considering trials as part of first-line treatment planning.
Will a clinical trial cost me money?
The study treatment and research-specific tests are typically covered by the trial sponsor at no cost to you. Routine care costs are billed to your insurance, and federal law requires most insurance plans to cover routine care during qualifying clinical trials. Some trials also offer travel reimbursement and other financial support. For more detail, see our guide to clinical trial insurance. Ask the trial site's financial coordinator for a clear breakdown before enrolling.
Can my oncologist help me find a trial?
Yes, and you should ask them directly. Your oncologist can recommend trials based on your specific diagnosis and treatment history. They can also help you evaluate a trial you've found on your own by reviewing the protocol and comparing it to your other options. If your oncologist isn't aware of relevant trials, databases and matching services can help fill the gap.
What does "randomization" mean, and should I be worried about it?
Randomization means that participants are assigned to treatment groups by chance — similar to a coin flip — rather than by choice. This is done to eliminate bias and produce reliable results. In cancer trials, all treatment groups receive at least the current standard of care, so randomization does not mean you risk going untreated. You'll know before enrolling whether a trial is randomized and what each treatment group involves.
How long do clinical trials last?
It varies widely. Some trials involve treatment for a few months, while others may last a year or more. Follow-up monitoring often continues after the treatment phase ends. The trial's informed consent document will explain the expected timeline, including how often you'll need to visit the trial site and for how long.
References
National Cancer Institute. "What Are Clinical Trials?" cancer.gov. https://www.cancer.gov/about-cancer/treatment/clinical-trials/what-are-trials
American Cancer Society. "Clinical Trials: What You Need to Know." cancer.org. https://www.cancer.org/cancer/managing-cancer/treatment-types/clinical-trials/what-you-need-to-know.html
U.S. Food and Drug Administration. "The Drug Development Process." fda.gov. https://www.fda.gov/patients/learn-about-drug-and-device-approvals/drug-development-process
U.S. National Library of Medicine. "Learn About Clinical Studies." ClinicalTrials.gov. https://clinicaltrials.gov/ct2/about-studies/learn
Daugherty CK, Ratain MJ, Emanuel EJ, Farrell AT, Schilsky RL. "Ethical, Scientific, and Regulatory Perspectives Regarding the Use of Placebos in Cancer Clinical Trials." Journal of Clinical Oncology. 2008;26(8):1371-1378. https://ascopubs.org/doi/10.1200/JCO.2007.13.5335
Unger JM, Vaidya R, Hershman DL, Minasian LM, Fleury ME. "National Estimates of the Participation of Patients With Cancer in Clinical Research Studies." Journal of Clinical Oncology. 2023. https://ascopubs.org/doi/10.1200/JCO.23.01030
Friends of Cancer Research. "Drug Approval Process." https://friendsofcancerresearch.org/glossary-term/drug-approval-process/
