The author illustrates the development of various “levels” of evidence by considering the evolution of less invasive surgical treatments for early breast cancer. He shows that the weight of evidence account explains the notion of levels of evidence and other efforts to rank them. In addition, he presents a defense of randomization as a method to maximize accuracy in the conduct of clinical trials. The title also considers ethical issues surrounding experimentation with medical therapies in human subjects. It illustrates and discusses these issues in studies of respiratory therapies in neonates and treatment for certain cancers in adults. The author shows that in many cases sufficient evidence can be accrued to warrant generally accepted new therapies without the need for evidence derived from randomized clinical trials.weiterlesen