Are there risks to participating in a clinical trial?

All treatments or interventions have potential risks, including treatments or interventions investigated in clinical trials. New treatments can have unknown side effects, or the assigned treatment may not work well for you. It is important to understand the risks and consider whether they are outweighed by the potential benefits. This is a personal decision—some people with cancer may feel that even a small chance of being helped is worth the risk, while others may not. Some people may feel the potential to help society by participating is worth the risk, while others may not. Your doctor can help you set expectations in terms of the benefits and risks you can reasonably expect. For many people, practical concerns related to costs, time, and travel also factor into decisions about the risks versus benefits of participating in a trial.

What are the risks of participating in a clinical trial?

While most available cancer treatments have significant side effects, a risk of participating in a clinical trial is that the new treatment may have unknown or more severe side effects than standard treatments that have already been tested in many people.

There is a risk that the new treatment or intervention may not work as well as the standard of care treatment, or that the assigned treatment may not work well for you, even if it helps others. You may receive a standard treatment during the trial, but later learn (based on results from the study) that the new treatment works better. This risk also exists outside of a clinical trial, and unfortunately, not all patients respond well to standard of care treatment.

For randomized clinical trials, where participants are randomly assigned to one of two or more treatments that are being compared to each other (for example, a new experimental treatment versus standard treatment), you and your doctor will not be able to choose which treatment you receive. In this case, you will need to be comfortable with the possible benefits and risks of all of the treatments that are being offered in the study and not just the new treatment or intervention.

There is a possibility that not all costs will be covered by insurance (see What are the costs of clinical trials?). It is important to speak with your clinical trial team and insurance provider before agreeing to participate in a clinical trial to make sure you understand what will be covered. Participating in a clinical trial may require more frequent medical office visits and testing, which can mean more time off of work or time spent away from family. Participants who are treated at a center in a different city may need to consider the time and costs associated with traveling to the treatment center. Some trials offer assistance with lodging and travel to participants who travel to participate in the trial.

Are clinical trials safe?

While steps are taken to keep participants as safe as possible (see below: How are patients protected?), clinical trials involve safety risks. During the informed consent process, you will learn about the possible side effects of the specific treatment or intervention, which may be similar to or different than standard treatments.

Even routine medical tests, procedures, and treatments are associated with some risk of side effects. This risk can be higher for a clinical trial because there are more unknowns—a new treatment or combination of treatments may cause unexpected or severe side effects that are not usually seen with standard treatments. This risk can be particularly true for earlier phase (phase I and II) trials, which usually test treatments that have been studied in fewer people.

An important part of most clinical trials is to learn about the side effects of a new treatment. Once you begin a trial, you will need to tell the research staff and your healthcare team as soon as possible about any side effects so that you can get treatment to relieve them and so the team can document your responses. You may need to stop the study treatment and receive standard care if the side effects become too severe. As discussed below, data safety monitoring boards continuously review the side effects in larger clinical trials and may stop a trial early if the new treatment causes severe side effects.

How are patients protected?

There are several safeguards to protect people who participate in clinical trials. While there are still risks involved in any study, as discussed above, these safeguards help keep everyone as safe as possible. Groups of experts set rules for clinical trials that must be strictly followed by the doctors and researchers. While a study is going on, the results are watched closely and the trial can be stopped early if needed, for example if there are safety concerns, if the new treatment is clearly much better (or worse) than the standard of care, or if a different, newer treatment is approved in the meantime that changes the standard of care.

Read more about how patients are protected in clinical trials.

What questions should I ask?

Before agreeing to participate in a clinical trial, you should understand as much as possible about the study. Asking questions can help you understand the risks versus benefits of participating in a clinical trial. Some of your questions may be addressed in the informed consent document (you can read more about informed consent here). You should feel comfortable asking your healthcare and research team questions about the risks, expected benefits, procedures, and costs.

If a treatment has been studied before, for example, in people with a different type of cancer, asking about what types of side effects those patients experienced may help you get an idea of what you might expect. For randomized studies, asking questions can help you be prepared for the possible side effects for any of the possible treatment possibilities.

It may help to jot down your questions before your doctor’s visit so that you are prepared.