What Clinical Trial Results Can Tell Us
Clinical trials can help us understand a medicine's potential benefits ("efficacy"or how well a medicine works for a specific disease) and risks ("safety"or side effects). They are often run before a new treatment or medicine is reviewed by the Food & Drug Administration (FDA) and are among the important information that the FDA considers when deciding whether to approve a therapy for use in people in the U.S. They are also typically reviewed when the FDA is considering a new use for an already-approved treatment or medicine.


Clinical trials can help us understand a medicine's potential benefits ("efficacy" or how well a medicine works for a specific disease) and risks ("safety" or side effects). They are often run before a new treatment or medicine is reviewed by the Food & Drug Administration (FDA) and are among the important information that the FDA considers when deciding whether to approve a therapy for use in people in the U.S. They are also typically reviewed when the FDA is considering a new use for an already-approved treatment or medicine.
- In this kind of research study, patients are ‘randomized,’ meaning that they are assigned at random (like flipping a coin) to different groups within the study (a randomized study can have 2 or more groups). This way the groups can be better ‘balanced’ so that who is in which group should not influence the results.
- ‘Controlled’ means that the study compares results for the group, or groups, of patients who are given the medicine being tested with results for the group (or groups) that is given something else or no treatment at all (called a control group).


At the end of the clinical trial (and sometimes during), the groups are compared based on the goals that were set before the study started to understand whether the medicine did what it was expected to do and whether there are any safety issues.
Clinical trials give us important information on the efficacy and safety of the medicine, but there are limitations to this type of study. Clinical trials take place under very controlled conditions and have strict rules on who can be included in the study. While these strict rules help us understand if the results that were seen were due to the medicine itself, they may not always represent ‘real-world’ situations or the larger population of people living with the disease being studied.


- RCTs are most often run before a treatment is approved by the FDA, so it can be prescribed to patients.
- Before a trial starts, researchers decide what data needs to be collected to answer specific questions based on the goals of the study. Researchers then collect the data throughout the length of the study so that it can be available for analysis when the study is completed (or sometimes during the study).
- When a trial is controlled, results for the specific group of people taking a medicine are compared to results for another group not taking that medicine.
What Real-World Evidence (RWE) Can Tell Us
Once a medicine is approved by the FDA and more people are using it, more information becomes available. RWE can provide more information on the experience patients have with the medicine in the ‘real world.’ Sometimes this additional information includes data relating to patients that are approved to use the medicine, but have characteristics that are more like those taking the medicine in the ‘real world.’


Once a medicine is approved by the FDA and more people are using it, more information becomes available. RWE can provide more information on the experience patients have with the medicine in the ‘real world.’ Sometimes this additional information includes data relating to patients that are approved to use the medicine, but have characteristics that are more like those taking the medicine in the ‘real world.’


- Information is gathered after a treatment is approved by the FDA and is being prescribed to patients in the U.S.
- The data that make up RWE are captured from everyday medical care. It can come from various sources, including electronic health records, pharmacy and insurance claims, and patient apps to better understand how patients are using and responding to a medicine once it has been approved for use. No patient names or identifying information are included in this data, so specific patients cannot be identified by the data collected.
- Real-world studies may choose to observe data from people who are similar, but the patient population in RWE can include other characteristics, which may not have been included in a clinical trial.


As a reminder, clinical trials remain the gold standard in the development of new medicines, or new uses for already-approved medicines. RWE cannot be directly compared with clinical trials. RWE offers information about a medicine in everyday use and may represent a broader population than those in the clinical trials. However, this data has limitations that are important to know:
- Real-world data are collected from various sources and may be incomplete because researchers can’t go back to collect missing information.
- In the real world, patients are not randomized, so there may be bias in the data collected.
- When considering RWE, remember that it's only based on the patients represented in the data source.
- Safety data may not be collected in real-world studies.
Start A Conversation With Your Doctor
Researching the data about treatment options may leave you with questions—and it’s important to get the answers you need. Talk to your doctor. Being informed can help you actively participate in decisions about your health.
Doctor Discussion Guide
Doctor Discussion Guide
Get the most out of your next visit with your healthcare team. Print out this list of questions to help start the conversation.
Get the most out of your next visit with your healthcare team. Print out this list of questions to help start the conversation.