What Are the Stages of a Clinical Trial?

One of the ways that researchers make clinical trials for cancer treatments safer is by breaking the trial into four stages. Each stage tackles a different goal, from proving safety to effectiveness.

“This is really a part of the effort to make sure that drug development is as safe as possible,” says June Y. Hou, MD, Gynecologic Oncologist at Columbia University’s Irving Medical Center.

Usually, people only participate in one stage of the trial. Some people choose to continue to another phase, such as if the treatment is working well for them.

Stage 1 of Clinical Trials

Stage 1 is looking to see if the treatment is safe. This occurs after animal testing. It involves around 15 to 30 participants, or sometimes up to 50. 

The small group allows doctors and researchers to monitor you closely. This allows them to detect any side effects or safety concerns early.

Along with watching for side effects, researchers also look to find the safe dose of the treatment. 

Stage 2 of Clinical Trials

Stage 2 is looking to see if the treatment is effective against a specific type of cancer or other illness. This involves a larger group of participants, usually 50 to 100 people.

In this stage, researchers will continue to look for side effects in participants.

Stage 3 of Clinical Trials

Stage 3 is looking to see if the new treatment works better, is equally effective, or has fewer side effects than the current treatments. In this phase, there may be hundreds or thousands of participants, possibly from around the world.

In stage 3, you may receive the new treatment or not. You and your care team may or may not know which group you are in. 

If stage 3 is a success, the manufacturer may then submit an application for FDA approval.

Stage 4 of Clinical Trials

Stage 4 occurs after FDA approval. It monitors the treatment’s long-term risks and benefits in the general population. This can help detect rare side effects that did not appear during stages 1, 2, and 3.

“The research team, including the pharmaceutical companies, are continuously interested in collecting safety data,” says Hou. 

Thanks to the phased approach of clinical trials, participants are better protected. Doctors catch side effects and find safe doses early on, and by starting with small groups, they can give patients extra-close attention. It’s all designed to make each step safer, and bring better treatments to more people.