COMMENTARY The Science of Improvement

IN THE EARLY 1890S, DR WILLIAM HALSTED DEVELOPEDradical mastectomy for breast cancer. Surgeons per-formed the Halsted procedure for more than 80 yearseven though there was little systematic evidence for its success. Then a new breed of scholars subjected the proce-dure to formal methods of evaluation unknown to Hal-sted.1 The methods—randomized controlled trials (RCTs) principal among them—led to a surprise: radical mastec-tomy had no advantage over simpler forms of treatment.2 This is but 1 example of the hard-won victory of evi-dence over belief in medicine. The pioneers of the formal evaluation of medical practices raised questions that tradi-tional practitioners did not welcome. But in time, formal evaluation prevailed.3,4 The pioneers developed a hierar-chy of evidentiary rigor relating the design of a study to the confidence that could be placed in the findings, from the lowly, nearly valueless anecdote to the royalty of evidence, the RCT