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Begg funnel plot for publication bias test. Plots are arranged as follows: (A) all 19 eligible studies (18 publications) for overall survival (OS); (B) 18 studies (17 publications) for OS in esophageal squamous cell carcinoma (ESCC); (C) all 12 eligible studies (11 publications) for disease-free survival (DFS); (D) 11 studies (10 publications) for DFS in ESCC.
