Pattern of lymph node metastases and its implication in radiotherapeutic clinical target volume in patients with non-small-cell lung cancer: a study of 2062 cases

Objective: To study the pattern of lymph node metastasis (LNM) of non-small-cell lung cancer (NSCLC) and to clarify which node level should be included while undergoing radiotherapy (RT). Methods: A total of 2062 patients with NSCLC patients who had undergone thoracotomy were retrospectively examined. The clinicopathological factors related to LNM were analysed. Results: The LNM rates (the number of node-positive patients/the total number of patients) in patients with primary tumours in different lobes (left upper lobe, left lower lobe, right upper lobe, right middle lobe and right lower lobe) were 53.25%, 53.87%, 53.77%, 64.67% and 61.58%, respectively. We have found that in all of the clinicopathological factors, including sex, age, tumour location, histological type, maximum diameter, T stage, degree of differentiation and tumour growth pattern, only maximum diameter (p=0.336) and histological type (p=0.360) did not have significant correlation with LNM rate. All of the above factors except tumour growth pattern (p=0.239) and maximum diameter (p=0.613) were significantly associated with lymph node ratio [LNR, ratio between metastatic and examined lymph nodes (LNs)] in linear regression. Conclusion: For patients with NSCLC, LNM rate and LNR can be recommended as applicable parameters for LN involvement. Multiple clinicopathological factors should be considered comprehensively to design the clinical target volume for RT of NSCLC. Advances in knowledge: This article can provide evidence to radio-oncologists how to choose range of lymph nodal clinical target volume when they are treating inoperable patients with NSCLC patients by analysing data of patients after surgery.