Cancer clinical trials include research at three different phases that usually progress in the same series of steps:

1. Phase I Trials: In Phase I trials, researchers test a new drug or treatment in a small group of people for the first time to evaluate its safety, determine a safe dosage range and identify any possible side effects. If Phase I trials show that a treatment is safe, the treatment moves on to Phase II.

2. Phase II Trials: Phase II trials are conducted to show that a new drug or treatment is effective. Researchers continue to monitor safety during Phase II trials, in addition to identifying which cancers are most successfully treated with the drug. A larger number of people are involved in these trials.

3. Phase III Trials: Phase III trials are used to compare the effectiveness of the new drug or treatment to those currently available (standard of care) to patients and to monitor side effects. Phase III trials enroll large numbers of participants—usually hundreds or thousands of people—in doctor's offices, clinics and cancer centers nationwide. Participants are randomly assigned to receive either the standard of care, or standard of care plus the new, possibly better treatment.