Pattern of 4L LN metastasis in left lung cancer and its influence on complete resection

Objective To introduce our experience of 4L lymph node dissection in left lung cancer and to analyze the pattern of 4L LN metastasis. To investigate the prognostic impact of 4L lymph node dissection. Methods 171 patients with left lung cancer who underwent pulmonary resection andsystematic mediastinal lymph node dissection from March 2016 to March 2019 were collected retrospectively. There were 106 males and 65 females endolled, aged(64.1±7.7) years. 54.4% had a history of smoking. The diameter of the tumors was(3.3±1.9) cm; Central-type tumor were 59 cases(34.5%), peripheral 112 cases(65.5%), upper lobe 95 cases(55.6%) and lower lobe 76 cases(44.4%). The clinical and perioperative data as well as the pattern of lymph node metastasis were analyzed. t test or Mann-Whiteney U test was used for continuous variables, and χ2 test or Fisher test was used for categorical variables. Multivariate analysis was performed using a logistic regression model to evaluate the risk factors. Results The metastasis rate of station 4L was 21.6%. Tumor size, locations(central type/upper lobe), operative type, micropapillary/entity components and vascular invasion were risk factors for 4L LN metastasis in univariate analysis. Tumor size(OR=1.611, P=0.032) and location of upper lobe(OR=2.823, P=0.008) were independent risk factors in multivariate logistic analysis. Through the analysis of ROC curve, the optimal cutoff point of tumor size was 2.5cm. The metastatic rate of 4L was 32.6% when tumor size larger than 2.5 cm and 7.9% when tumor size smaller than 2.5cm.Tumor located in upper lobe tended to metastasize to upper mediastinal lymph nodes, including station 4L, 5 and 6, while the one located in lower lobe tended to metastasize to station 7. Conclusion Station 4L LN involvement is commen in left lung cancer. The dissection of the 4L LN is important, especially for the tumor larger than 2.5 cm or located at upper lobe. Key words: Lung tumor; Lymph node metastasis