Background: Peripheral monocyte count is an assessable parameter. Recently, evidence suggested an elevated preoperative monocyte counts predicting poor prognosis in malignancies. The aim of this study was to determine the prognostic effect of early postoperative (within 4 days) blood monocyte count in patients with lung adenocarcinoma or squamous cell carcinoma following lobectomy. Methods: We retrospectively reviewed patients with operated lung adenocarcinoma or squamous cell carcinoma from 2006 to 2011 in Western China Lung Cancer database. Both the preoperative and postoperative monocyte counts were divided into two groups. Univariate analysis on disease-free survival (DFS) and overall survival (OS) was performed using the Kaplan-Meier and log-rank tests, and multivariate analysis was conducted using the Cox proportional hazards regression model. Results: There were 433 patients enrolled in our analysis. The cut-off values were 0.375*109/L and 0.845*109/L for preoperative and early postoperative monocyte count respectively which were calculated by receiver operating characteristic curve. Two-tailed log-rank test indicated patients with an early postoperative elevated monocyte count predicted a poor DFS and OS overall (P<0.001, P<0.001, respectively) as well as in subgroup analysis. On univariate and multivariate analysis, early postoperative elevated monocyte count presented as a promising independent prognostic factor for both DFS and OS (HR=2.991, 95%CI: 2.243-3.988, P<0.001; HR=2.705, 95%CI: 1.977-3.700, P<0.001, respectively). However, no significance was detected for preoperative monocyte in multivariate analysis. Conclusions: Elevated early postoperative peripheral monocyte count is an independent predictor of poor prognosis for patients with operable lung adenocarcinoma or squamous cell carcinoma by lobectomy.

High Postoperative Monocyte Predicts Worse Lung Adenocarcinoma or Squamous Cell Carcinoma Outcomes