Clinical Trial Presentations, Agency Guidelines, and Oncology Practice: Findings from the Arimidex, Tamoxifen, Alone or in Combination Trial

PurposeOur objective was to explore the potential influence of agency guidelines/technology assessments regarding anastrozole use in clinical practice in the United States and European Union, based on findings related to the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial.Patients and MethodsWe examined temporal relationships among ATAC-related oral data presentations, peer-reviewed publications, regulatory agency approvals and agency guidelines/technology assessments to the patient days' use of anastrozole in the United States and European Union.ResultsAnastrozole usage increased at a relatively constant rate following oral presentations of ATAC results at oncology congresses and did not appear to be strongly influenced by publications or agency guidelines/technology assessments, which appeared to lag rather than lead clinical usage.ConclusionThe presentation of clinical trial data at large international congresses rapidly changed anastrozole use in clinical practice regardless of ongoing guideline recommendations. This observation raises the following question: Have clinicians adopted adjuvant anastrozole use prematurely? Or, is the level of evidence required by expert panels higher than that with which oncologists in clinical practice are comfortable?