Prognostic impact of preoperative monocyte counts in patients with resected lung adenocarcinoma.

Increasing evidence suggests that an elevated peripheral monocyte count at presentation predicts a poor prognosis in various types of malignancy, including malignant lymphoma. In lung adenocarcinoma, tumor-associated macrophages (TAMs) were reported to be associated with a poor prognosis. However, it is unknown if an elevated peripheral monocyte count is associated with a poor prognosis in lung adenocarcinoma. This study assessed the prognostic impact of the preoperative peripheral monocyte count in lung adenocarcinoma. We retrospectively analyzed 302 consecutive patients with lung adenocarcinoma who received curative resection at Kitano Hospital. The receiver operating characteristic (ROC) curve for the peripheral monocyte count was used to determine the cut-off value. The relations between peripheral monocyte counts and clinicopathological factors were assessed. We also evaluated the impacts of possible prognostic factors including the preoperative peripheral monocyte count on survival, using the two-tailed log-rank test and Cox proportional hazards model. In addition, immunohistochemical staining for CD68 was performed to evaluate the monocytes in primary tumors. A peripheral monocyte count of 430mm(-3) was the optimal cut-off value for prognosis. An elevated peripheral monocyte count was significantly associated with sex, performance status, smoking history, chronic obstructive pulmonary disease and interstitial lung disease. The two-tailed log-rank test demonstrated that patients with an elevated peripheral monocyte count experienced a poorer recurrence-free survival (RFS) and overall survival (OS) (P=0.0063, P<0.0001, respectively). In the multivariate analysis an elevated peripheral monocyte count was shown to be an independent prognostic factor for the RFS and OS (HR: 1.765; 95% CI: 1.071-2.910; P=0.0258, HR: 4.339; 95% CI: 2.032-9.263; P=0.0001, respectively). Furthermore, numbers of the monocytes in primary tumors significantly correlated with peripheral monocyte counts (r=0.627, P<0.0001). The preoperative peripheral monocyte count is an important prognostic factor for patients with lung adenocarcinoma after curative resection.