Clinical Trials 101

Clinical Trials 101

Reviewed by Jasper Clinical Board

Last updated 5/24/21

Many people with cancer are curious about clinical trials (though currently fewer than 1 in 20 eligible patients sign up) but the idea of taking part in one is likely to bring up a variety of feelings, questions, and concerns. Some people want to gain access to promising new treatments. Others may be worried about the risks or want to avoid feeling like a “guinea pig.” For still others, taking part in clinical trials is a way to connect their experience of cancer to something larger and help future patients by contributing to the advancement of research and treatments. 
All of these feelings—even a mixture of them—are completely normal! And ultimately only you can decide whether participating in a clinical trial makes sense for you. Here’s what you need to know to make well-informed decisions about cancer-related clinical trials.

How clinical trials work

Clinical trials provide the information researchers need to determine the best ways to prevent, diagnose and treat cancers. The government also relies on this information to approve new therapies. Clinical trials drive progress in medicine—they are the tools that improve standard approaches to an illness over time. 

Trial phases

Clinical trials occur in several phases. Phases 1-4 are the most common, although in some cases a treatment might include an earlier phase, called an “Early Phase 1” trial (in the past this was sometimes called a Phase 0 trial). 
Early Phase 1 trials are very small, in terms of both the number of participants and the time period. They include very minimal human exposure to new drugs and are just meant to test whether or how a drug acts in the body. In Early Phase 1 trials, the dose of the drug is very low and isn’t meant to have any therapeutic benefit. These studies can help researchers ensure a new therapy holds promise before continuing to further trials.   
Phase 1 trials for new therapies focus on safety and usually include a small number of healthy participants (unless the drug is to be used exclusively for cancer, in which case it can only include cancer patients). Their main purpose is to reveal any side effects. 
If Phase 1 trials reveal no major safety issues, a treatment can progress to Phase 2. In Phase 2, researchers look for signs that a treatment works, and they continue to watch for any short-term side effects. Phase 2 trials include more participants than Phase 1 trials. 
If a treatment continues to demonstrate promise and safety in Phase 2, then it can move onto Phase 3. Phase 3 clinical trials are larger, more definitive studies involving greater numbers of people. The results of Phase 3 trials are crucial in earning a new therapy approval from the Food and Drug Administration. 
Phase 3 trials may compare several different treatment options, such as different doses or different combinations of therapies. They might study a particular therapy in several different populations (men, women, older, younger, etc.). These trials are usually randomized, meaning that the people taking part in them are assigned to treatment groups by chance. If a study is “blind,” participants don’t know which treatment they’re receiving (however, they do know the possible treatments they could get and in cancer clinical trials patients will always receive a treatment believed to be at least as good as the current approved treatment). 
Phase 4 trials happen after the FDA approves a therapy. These trials might look at long-term outcomes and side effects of treatment, or look for the best way to administer a therapy. 

What about placebos?

A placebo is an inactive substance or other treatment that’s given to a patient in the same way as an active therapy. The most well-known example is a sugar pill instead of a pill containing a drug. There can also be placebo injections, intravenous infusions, and other medical procedures. Because people’s beliefs and experiences with a treatment may influence the outcome, placebos help ensure that the psychological factors are the same in experimental and control groups during a clinical trial. 
Many people with cancer worry that if they participate in a clinical trial, they might be given a placebo instead of an active therapy. This is unethical for obvious reasons and it’s not permitted in clinical trials. People with cancer who participate in studies will always receive either the standard treatment for their condition or an experimental therapy researchers are investigating because they believe it may be more effective or have some other benefit over the current standard treatment (also called the “standard of care”).  
There are only certain, rare cases when a cancer patient might receive a placebo during a clinical trial. One situation would be if the trial is studying an existing therapy plus a new therapy in combination. In that case, you might receive both the existing therapy and the experimental therapy, or you might get the existing therapy along with a placebo. 
The only time when a cancer patient might receive only a placebo during a trial is when there is no existing treatment known to be effective for their cancer. In this case, a trial could compare the current “standard of care” (no treatment) to the experimental therapy. This situation is rare but if the clinical trial worked this way, you would be told in advance so that you could decide whether or not to participate. 

Informed consent

To adhere to medical ethics guidelines and regulations, researchers must always gain “informed consent” from study participants. This means that someone must explain the study’s potential benefits and risks to you and that you must sign paperwork indicating that you understand them before you can take part in the trial. 
Informed consent is a legal process, but it’s more than that. It provides a space for you to learn about a study’s purpose and design, request reading material and ask plenty of questions, so that you can weigh the pros and cons of participating for yourself. 
Clinical trials are always voluntary. No one can make you participate if you don’t want to—even if the trial has already started. You can withdraw your consent and quit the trial at any time. 
During the informed consent process, you’ll connect with a representative of the trial. Usually that person is a nurse who is acting as the trial’s research coordinator. Sometimes it’s the principal investigator (PI), or main organizer of the trial. Either way, that person will give you a document called the study protocol, which includes information about the purpose, design and scale of the study, the different treatments used, potential risks and benefits, and what kinds of tests or exams you’ll need to get if you decide to participate. (Often, taking part in a clinical trial involves more tests—lab work, scans, etc.—than you might get as part of standard treatment.) 
The research coordinator will review all this information with you to make sure you understand it. They will expect you to have questions and you should not hesitate to ask them anything you’d like to know. You will have time to read the information on your own and discuss it with others if you like—such as your current healthcare team, family, friends or other doctors—before you agree to participate. 


Although the purpose of clinical trials is to report findings to the larger research community and the public, medical ethics guidelines ensure the privacy and confidentiality of participants. Your name and identifying information is removed from your medical information and replaced with a number for purposes of data analysis, so you will remain anonymous in any results. Feel free to ask the research coordinator of a clinical trial for more specific information about how they plan to safeguard your privacy. 


Clinical trials set eligibility criteria for participants, usually based on age, gender, type and stage of cancer, previous treatment and other medical history. Extensive previous treatment sometimes makes a person ineligible for a clinical trial. If you know you would like to take part in a study, it is a good idea to look into this earlier in the course of your cancer treatment to make it more likely you’ll be accepted into a trial. Some studies look specifically at therapies for recurrence of cancer and others track patients’ long-term outcomes. 


All clinical trials include some risk, just as all standard treatments and medical procedures carry a risk of side effects or ineffectiveness. As a general rule, the more that is already known about a therapy, the more information you will have to work with in understanding its risks. A later-phase clinical trial for a new therapy will mean there’s information already gathered from previous trials about the therapy’s safety record and side effects.
A useful way of thinking about clinical trials for new therapies is that the standard treatment comes with a well-known profile of its likely benefits and risks, while the experimental therapy carries a potential for greater benefit along with more unknowns about its risks. Both treatment approaches include some level of uncertainty for individual patients. The experimental therapy may provide more benefit—that’s why researchers are studying it—but there’s also greater risk involved since less is known about it overall. 
Be sure to find out about the risks of participating in any specific clinical trial during the informed consent process. 


Usually, your health insurance will cover any care you get as part of a clinical trial that would normally be a part of standard treatment for your cancer, while the organizers of the clinical trial will cover costs of experimental therapies or additional tests or exams. However, there can be exceptions and gaps, especially if you’ll be getting care at a facility or with healthcare providers who aren’t in your insurance company’s “network.” Sometimes clinical trials will cover costs that your insurer won’t in order to facilitate your participation. 
Be sure to check with both your insurance company and the study’s research coordinator about which costs each will and won’t cover. If you have to travel for the trial, there may be other expenses, like gas, parking, meals or hotel stays. If you’re concerned about these, feel free to ask if the clinical trial is willing to cover these costs for you. 

Weighing the pros and cons of joining a clinical trial

Deciding whether to participate in a clinical trial can be complex, with many different factors to take into consideration. Listing the potential benefits and drawbacks and then asking questions to understand each factor better for the particular trial you’re considering can help you gather the information you need and feel more confident about your decision. 
The general points below can be a helpful starting point for weighing the pros and cons of participating in a clinical trial.

Potential benefits

  • Access new and possibly more effective therapies, or therapies thought to offer better side effect profiles and quality of life for patients
  • Feel good about helping others and advancing cancer research
  • Receive more attention and interaction with medical staff 
  • Gain greater insight into your cancer and health care
  • Feel like you’re taking a more active role in your care

Potential drawbacks

  • A greater level of uncertainty about which treatment you are receiving (if the trial is blind and randomized) and its effectiveness and side effects
  • Potentially having to switch your care from a doctor or team you’re familiar with to the clinical trial’s healthcare team
  • A greater time commitment; more tests and exams
  • Potentially more travel
  • Any costs not covered by insurance or clinical trial
  • No guarantee you’ll get the experimental therapy
  • The risk that an experimental therapy won’t be as effective as researchers think or hope

Finding clinical trials

If you are interested in exploring clinical trials, don’t wait for your healthcare team to bring it up. Often, doctors don’t mention clinical trials unless they are involved in one or are aware of studies taking place at their institution. However, if you express interest, they may be able to help you gather information or make helpful connections. 
There are also several resources you can check for clinical trials without your doctor’s help: 
Research institutions and hospitals in your region are a good place to start if you want to find trials happening nearby. You can also contact research centers outside your area or check their websites if you’re willing to travel. 
Lastly, pharmaceutical companies’ websites have information about clinical trials for therapies they’re developing. This could be helpful if you are already aware of an experimental treatment you want to try and know which company makes it. 

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