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Funnel plots evaluating potential publication bias among the included studies. (a) Overall survival. (b) Disease-free survival. (c) Gender. (d) TNM stage. (e) Tumor differentiation. (f) Lymph node metastasis. (g) Distant metastasis. (h) Invasion depth. (i) Lauren's classification. (j) Vascular invasion. The circles represent an individual study enrolled in the present meta-analysis.
