Clinical trials help advance care and research. This page explains what clinical trials are, the different types of studies, and what the trial phases mean for patients and families.

What is a Clinical Trial?

A clinical trial is a research study that helps doctors and scientists learn more about a disease and improve care. Clinical trials may test new treatments, study how a condition progresses, or collect information to improve diagnosis, symptom management, and quality of life.

For people affected by complex lymphatic anomalies (CLAs) and lymphatic malformations (LMs), clinical trials play an important role in advancing understanding of these rare conditions and developing better treatment options.

Participation in a clinical trial is always voluntary. Clinical trials are one option for care, but they are not required for all treatments. While some new or investigational medications may only be available through a clinical trial or special access program, many patients receive care without ever joining a trial.

Clinical trials vary widely. Some involve treatment, while others are observational and do not include experimental therapy. Not every patient will qualify for a clinical trial, and not qualifying does not reflect disease severity or limit access to standard care.

Deciding whether to participate in a clinical trial is a personal choice and should be discussed with your healthcare team.

Types of Clinical Trials

Not all clinical trials are the same. Different types of studies are designed to answer different questions about a condition and its care. Understanding the type of trial can help you know what participation may involve.

Treatment trials test new medications, procedures, or approaches to care. These studies look at how well a treatment works and what side effects may occur. Some treatment trials involve medications that are not yet widely available.

Observational studies do not involve experimental treatment. Instead, researchers collect information over time—such as symptoms, imaging, lab results, or quality-of-life measures—to better understand how a condition develops and affects patients.

Natural history studies are a type of observational study that track how a condition changes over time without altering treatment. These studies are especially important in rare diseases, where understanding disease progression can help guide future research and care.

Registry studies collect health information from many individuals to identify patterns and improve understanding of rare conditions. Participation often involves sharing medical records or completing surveys and may be done remotely.

Some studies involve minimal participation, while others may require clinic visits, testing, or travel. Your healthcare team or study coordinator can help explain what participation would look like for a specific trial.

What Are the Phases of a Clinical Trial?

Clinical trials are often conducted in phases, or stages. Each phase has a different goal and helps researchers answer specific questions about a treatment. Understanding trial phases can help set expectations about what participation may involve.

Phase 1 trials focus on safety. These studies involve a small number of participants and help determine how a treatment behaves in the body, what dose is safe, and what side effects may occur. In rare diseases, Phase 1 trials may include patients who are directly affected by the condition.

Phase 2 trials look at how well a treatment works while continuing to monitor safety. These studies usually include more participants and provide early information about whether a treatment may be effective for a specific condition.

Phase 3 trials compare a new treatment to standard care or to a placebo. These studies involve larger groups of participants and help confirm effectiveness, monitor side effects, and gather information needed for regulatory review.

Some studies may also include a Phase 4, which takes place after a treatment has been approved. These trials collect additional information about long-term safety, effectiveness, or use in broader patient populations.

It’s important to know that later phases do not always mean a trial is “better” or more appropriate for an individual patient. Each phase carries different potential benefits and risks. Your healthcare team can help you understand which phase, if any, may be appropriate based on your diagnosis, symptoms, and treatment goals.