Retrospective Propensity Score Matching and the Selection of Surgical Procedures: How Precise Can a Propensity Estimate Be?

TO THE EDITOR: An article by Kim et al 1 was recently published comparingthesurgicalandoncologicoutcomesbetweenlaparoscopic andopengastrectomyforgastriccancer.Theauthorsusedpropensity scorematchingtominimizetheselectionbiasinaretrospectivecohort of patients from multiple centers. Kim et al tried to adjust for confounding factors by using propensity score matching, and they concluded that laparoscopic gastrectomy for gastric cancer seems comparable with open surgery. However, we have several significant concernsaboutthecase-matchingmethodthatwasusedinthisstudy. The propensity score analysis was developed to minimize the differences in patients’ covariates, which could become confounding factors in the examination of treatment effects in observational stud