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When we think of clinical trials, we often picture early-stage testing in labs or hospitals. But what happens after a drug gets approved by the U.S. Food and Drug Administration (FDA) and is available for use?
Phase 4 studies, also known as post-marketing surveillance trials, help us understand how a treatment performs in the real world, outside of tightly controlled trial settings. They ensure long-term safety, discover rare side effects, and offer insights that influence how drugs are prescribed for years to come.
For rare and difficult-to-treat cancers like mesothelioma, they can be crucial to helping doctors prescribe the therapies to their patients.
What Is a Phase 4 Clinical Trial?
A phase 4 clinical trial takes place after a drug or medical device has been approved by regulatory bodies like the FDA. While earlier clinical trials for mesothelioma test whether a drug works and is safe, phase 4 explores how well it continues to work and how safe it is in much broader, daily use.
Why Phase 4 Clinical Trials Are Important
Even after a drug is approved, there’s still more to learn. Phase 4 studies help answer key questions:
- How does the treatment work in the general population, including older adults, children or people with other health conditions?
- Are there any rare or long-term side effects not visible in earlier, smaller studies?
- Can the treatment be improved by changing dosage, timing or combination with other drugs?
- How does real-world effectiveness compare to results seen in clinical trials?
What Is Learned in Phase 4 Clinical Trials?
Long-Term Safety
Drugs may show no major side effects in early trials, but some complications only appear after months or years of use. Phase 4 clinical trials monitor long-term risks, such as liver damage, cardiovascular events or cognitive changes.
Real-World Effectiveness
Does the therapy work beyond those selected for clinical studies? For example, a specific treatment for mesothelioma might work well in a carefully selected group during phase 3 but less effectively in the general public. Phase 4 reveals how it performs in diverse, everyday settings.
Drug Interactions and Off-Label Uses
Post-marketing trials can uncover how a drug interacts with other medications or how it performs when used for conditions it wasn’t originally approved for.
Comparative Data
Sometimes, phase 4 trials compare the new drug against other available treatments to see which works better in practice.
Efficacy Versus Safety in Phase 4
Phases 1-3 clinical trials focus on both efficacy (does the treatment work?) and safety (is it harmful?), but phase 4 leans more heavily on safety monitoring over time.
That said, phase 4 clinical trials may continue to evaluate a drug’s effectiveness in broader or niche populations, ensuring it benefits patients in the way it was intended.
How Many Patients Are Involved in Phase 4 Studies?
There’s no one-size-fits-all number, but phase 4 trials typically include thousands of participants. Since they are often observational or registry-based studies, they can include large, diverse populations across multiple regions or even countries.
The size depends on the:
- Rarity of the condition
- Goals of the study
- Likelihood of detecting rare side effects
- Whether it’s an active trial (new study) or a registry (tracking outcomes over time)
In the case of rare diseases such as mesothelioma, phase 4 studies are often observational or registry-based, typically involving 100-200 patients, especially when monitoring newly approved therapies. An example is recent approval of immunotherapy for mesothelioma: Opdivo and Yervoy, two immune checkpoint inhibitors.
Larger-scale post-marketing data gathering remains rare due to the disease’s low incidence and limited marker reach.
Why Should Patients and Providers Care About Phase 4 Clinical Trials for Mesothelioma and Other Types of Cancer?
Phase 4 clinical trials may fly under the radar compared to earlier phases since the therapies are already approved and the public does not follow the results as much, but they play a critical role in public health. They ensure that a drug that works well in clinical trials continues to work safely in the real world where life is unpredictable, complex, and rarely follows the perfect protocols of early studies.
If you’re ever prescribed a newly approved medication, chances are you’re contributing to phase 4 knowledge by helping improve treatment not only for yourself, but for patients worldwide.
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