Phase 1 (phase I) trials study whether a new treatment is safe to use over a range of doses. The treatment may be given to people with different types of cancers.
A phase 1 trial is mainly a drug safety study.
Phase 2 (phase II) trials study how well a treatment works for a certain cancer, such as breast cancer. These trials may include between 25 and 100 people.
After a drug (or other therapy) is found to be effective in treating breast cancer in a phase 2 trials, a phase 3 trial will study it further.
Phase 3 (phase III) trials study how well a new treatment (including surgical procedures) works compared to the standard treatment (standard of care).Phase 4 (phase IV) trials study the long-term side effects of treatments or answer new questions about the treatment.