The science of learning from improvement

In the early 1890s, Dr. William Halsted developed radical mastectomy for breast cancer. Surgeons performed the Halsted procedure for more than 80 years even though there was little systematic evidence for its success. Then a new breed of scholars subjected the procedure to formal methods of evaluation unknown to Halsted. The methods- randomized controlled trials (RCTs) principal among them- led to a surprise: radical mastectomy had no advantage over simpler forms of treatment. This is but one example of the hard-won victory of evidence over belief in medicine. The pioneers of the formal evaluation of medical practices raised questions that traditional practitioners did not welcome. But in time, formal evaluation prevailed. The pioneers developed a hierarchy 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. (March 3, 2008)