A clinical trial is a carefully designed study that evaluates new drugs, devices or care strategies in eligible patients who choose to participate. A clinical trial typically compares a new approach with the current standard of care to determine whether it leads to better outcomes. If it does, it may become part of routine medical practice.

Each phase serves a distinct purpose. Phase I focuses on safety, helping researchers determine whether a new treatment can be used safely in people.

Phase II evaluates whether the treatment shows signs of effectiveness, often by comparing before and after images or blood test results.

Phase III tests whether the treatment improves patient outcomes—such as reducing heart attacks, lowering mortality or improving quality of life—and is required for U.S. Food and Drug Administration approval.

Phase IV trials occur after FDA approval and involve larger populations to monitor long-term safety and effectiveness, including the identification of any side effects.

Patient safety is a top priority. Participants must provide informed consent, meaning they fully understand the study and agree to participate. Studies follow strict ethical standards and are closely monitored by our Institutional Review Board to protect patient wellbeing. Patients enrolled in clinical trials often benefit from enhanced care because they are monitored more closely, with ongoing visits, tests and follow-up.

Each study has specific eligibility criteria to make sure the treatment is appropriate and safe for participants. For example, some trials may exclude patients with certain underlying conditions if they may be at increased risk or if they have little probability for benefit.

Because of these criteria, trial results apply most directly to the group of patients who were studied. Doctors then use their clinical judgment to decide how those findings may apply to patients in real-world settings.

Some trials use a placebo, an inactive treatment designed to resemble the real one. In these studies, the patient and the doctor are often unaware of who receives the actual treatment, a process known as “blinding.” Placebo-controlled trials are considered the most reliable way to understand whether a treatment truly works because they help reduce bias, ensuring that expectations don’t influence the results.

A placebo is not possible in some clinical trials. An example is when surgical procedures are being compared. In those cases, researchers rely on other methods to evaluate outcomes.

Yes—in most cases, tests, treatments or procedures that are part of the study are provided at no additional cost to participants.

Up to half of clinical trials at Cedars-Sinai focus on cancer, and the others are specific to other conditions. Participation tends to be higher in trials for serious or life-threatening diseases, where patients may seek access to innovative therapies that could improve or extend their lives.

Beyond the potential individual benefit, participants play an important role in advancing medical knowledge. Many of today’s standard treatments are the result of clinical trials made possible by patients who volunteered to participate. They’re the true heroes.

Cedars-Sinai offers an online registry where patients can search for studies by condition. Physicians are also informed about available studies and can help determine whether a trial may be a good fit. For most patients, the best first step is a conversation with their healthcare provider to explore whether a clinical trial is an appropriate option.