With early, obvious benefit of a targeted cancer drug, should expensive clinical testing continue?

Generally, FDA-approved clinical trials progress through three phases: the first shows safety, the second starts to explore effects and the third seeks to prove a drug's superiority over existing treatments. But when a drug's benefit is obvious in the first or second phase, is the third, costly phase needed? The question is posed in a recent edition of the journal Nature Reviews: Clinical Oncology by Robert C. Doebele, MD, PhD, investigator at the University of Colorado Cancer Center and assistant professor of medical oncology at the CU School of Medicine.