BackgroundSerum CYFRA 21–1 is one of the most important serum markers in the diagnosis of non-small cell lung cancer (NSCLC), especially squamous-cell carcinoma. However, it remains unknown whether pretreatment serum CYFRA 21–1 values (PCV) may also have prognostic implications in patients with advanced lung adenocarcinoma.MethodsWe retrospectively reviewed the data of 284 patients (pts) who were diagnosed as having advanced lung adenocarcinoma and had received initial therapy.ResultsOf the study subjects, 121 pts (43%) had activating epidermal growth factor receptor (EGFR) mutations (Mt+), while the remaining 163 pts (57%) had wild-type EGFR (Mt-). Univariate analysis identified gender (male/ female), ECOG performance status (PS) (0-1/ ≥2), PCV (<2.2 ng/ml/ ≥2.2 ng/ml), EGFR mutation status (Mt+/ Mt-), pretreatment serum CEA values (<5.0 ng/ml/ ≥5.0 ng/ml), smoking history (yes/ no) and EGFR-TKI treatment (yes/ no) as prognostic factors (p = .008, p < .0001, p < .0001, p < .0001, p = .036, p = .0012, p < .0001 respectively). Cox's multivariate regression analysis identified PCV < 2.2ng/ml as the only factor significantly associated with prolonged survival (p < .0001, hazard ratio: 0.43, 95% CI 0.31-0.59), after adjustments for PS (p < .0001), EGFR mutation status (p = .0069), date of start of initial therapy (p = .07), gender (p = .75), serum CEA level (p = .63), smoking history (p = .39) and EGFR-TKI treatment (p = .20). Furthermore, pts with Mt+ and PCV of <2.2 ng/ml had a more favorable prognosis than those with Mt+ and PCV of ≥2.2 ng/ml (MST: 67.0 vs. 21.0 months, p < .0001), and patients with Mt- and PCV of <2.2 ng/ml had a more favorable prognosis than those with Mt- and PCV of ≥2.2 ng/ml (MST: 24.1 vs. 10.2 months, p < .0001).ConclusionPCV may be a potential independent prognostic factor in both Mt+ and Mt- patients with advanced lung adenocarcinoma.