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Cutoff value of pre-CEA. Nonsmoker group were ranked according to increased pre-CEA level and a maximum difference in distant metastasis-free survival was determined with pre-CEA level = 6.6 ng/mL in nonsmoker group (A) and 11.4 ng/mL in smoker group (B). pre-CEA=pretreatment serum carcinoembryonic antigen.
