Substantial imbalance that is never eliminated with propensity score matched analyses in comparing surgery to stereotactic body radiotherapy for patients with early-stage non-small cell lung cancer.

Competing Interests: Conflicts of Interest: Dr. A Takeda reports receiving a Varian research grant and a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science when conducting this study. The other authors have no other conflicts of interest to declare.