Preoperative monocyte count is a predictor of recurrence after Stage I lung adenocarcinoma resection

OBJECTIVES: High-grade tumours are observed even in Stage I lung adenocarcinomas. Tumour spread through air spaces (STAS) is a risk factor for recurrence after resection. However, there is no ideal predictive biomarker for STAS in high-grade Stage I lung adenocarcinoma. This study assessed the prognostic impact of the preoperative peripheral monocyte count in lung adenocarcinoma. METHODS: We retrospectively analysed the data of 444 patients with resected Stage I lung adenocarcinoma during 2006–2016. Univariable and multivariable Cox proportional analyses of recurrence-free probability (RFP) and overall survival (OS) were used to analyze preoperative complete peripheral blood cell count data. Since monocyte count was associated with poor prognosis, the relationship between preoperative peripheral monocyte count and clinicopathological factors, including STAS, was assessed. In addition, immunohistochemical CD68 staining was performed to evaluate tumour-associated macrophages (TAMs). RESULTS: A higher preoperative peripheral monocyte count was a predictor of lower RFP (P = 0.004) and lower OS (P < 0.001). In multivariable analysis, a higher peripheral monocyte count was an independent prognostic factor for RFP and OS (hazard ratio: 1.88, 95% confidence interval: 1.07–3.31, P = 0.029; hazard ratio: 2.13, 95% confidence interval: 1.22–3.75, P = 0.008, respectively). A higher peripheral monocyte count was associated with a higher frequency of STAS (P = 0.017) and higher number of CD68+ TAMs (P = 0.013). CONCLUSIONS: A higher preoperative peripheral monocyte count was an independent marker for a poor prognosis in Stage I lung adenocarcinoma and was associated with a higher frequency of STAS.