New cancer treatments and cancer drugs are first tested in the laboratory. They then go through three phases of tests with patients before they can been approved for use. They must be approved in each phase before going on to the next one.

The treatment is tested on a small group of patients when no other standard treatment exists to help them. This is to see what effect the treatment has on the body and what is the best dose.

1. The treatment is tested on a larger group of patients to see what kinds of cancer it can be used for. Also, possible side effects and dose levels are investigated.
2. The treatment is tested on a large group of patients. It is compared to the standard treatment available to see if it works better.
3. A license for the drug or treatment is requested once it has been approved in trial phase 3. Drugs under license can begin to be used in clinical practice.
4. This phase starts after approval and investigates the long-term risks and benefits.