Clinical trial design in metastatic breast cancer: a commentary.

Trial designs traditionally used in the development of new anti-cancer agents are usually categorized as phase I, phase II, phase III and phase IV. Such trials are often performed in patients with metastatic cancer. Phase I trials are conducted in small numbers of patients to determine a drug's maximally tolerated dose (MTD) and toxicity profile. In phase II studies, the anti-tumor activity of the new agent is tested in different tumor types. If a drug is found to be promising in phase II studies, it is then compared to standard therapy through a randomized trial design in phase III studies. In phase IV studies, the efficacy and safety profile of the drug are evaluated in a standard clinical setting. In the field of oncology, studies have been conducted in which agents already approved by the regulatory agency are combined with other anti-cancer drugs and evaluated for anti-tumor efficacy. These have also been termed phase II studies.