Author reply

摘要

The letter by Lee and McKenzie in response to our article has drawn readers' attention to the challenges of interpreting and comparing findings from observational studies. The authors quote highly variable outcomes from two observational studies examining the risk of cardio-toxicity in trastuzumab-treated patients, with incidence rates ranging from 3% to 39%. Conflicting observational evidence is not surprising, given the heterogeneity in study designs, including variations in patterns of care of the study population, outcome definitions and the characteristics of populations under study. For example, the differences observed in the studies cited by Lee and McKenzie may, in part, be attributable to exposure to different treatment regimens (37% of the first study cohort were exposed to anthracyclines in contrast with 87% of the second-cohort).