Evidence-based medicine: its effect on treatment recommendations as illustrated by the changing role of postmastectomy irradiation to treat breast cancer

PURPOSE: To illustrate the effect that the quality of evidence has on clinical practice, we examined how the role of radiotherapy in treating breast cancer has changed over the years as the quality of evidence evolved from anecdotal evidence based on expert opinion to randomized clinical trials and meta-analyses. METHODS: We searched the medical literature for key randomized studies and meta-analyses that have influenced the clinical use of postmastectomy irradiation since the first randomized trials in breast cancer in the 1950s. We discuss how clinical practice changed based on the outcomes of these trials, and then discuss the quality of those trials based on the criteria currently used to assess evidence from randomized trials (CONSORT) and meta-analysis (QUORUM). RESULTS: Evidence published from the early trials and meta-analyses on the role of postmastectomy irradiation had a strong effect on clinical practice. Examination of these studies, however, continues to show significant flaws in trial design that, by today's evidence-based standards, would not meet standards of quality. CONCLUSION: The quality of evidence has a strong effect on shaping clinical practice and needs to be continually assessed. Current guidelines developed to critique both individual randomized trials and meta-analyses are helping to establish high standards for trial design and interpretation. Evidence from older trials that were not guided by well-developed guidelines need to be reviewed, particularly when results from those trials are continually updated and used to generate evidence on which to base current clinical practice.