Trial phases in simple words

A new treatment is tested step by step. Each step is called a phase.

Phase 1 and 2

• Phase 1: is it safe, and what dose is right? A small number of people
• Phase 2: does it work against this cancer? More people

Phase 3 and 4

• Phase 3: is it better than the usual treatment? Many people, often in many hospitals
• Phase 4: studied further after approval

Remember

• Every phase has its own possible benefits and risks
• Ask the trial team to explain them

Sources

• National Cancer Institute: Phases of clinical trials