Tumor Primary Location May Affect Metastasis Pattern for Patients with Stage IV NSCLC: A Population-Based Study

BACKGROUND: Most patients with nonsmall cell lung cancer (NSCLC) were initially diagnosed with distant metastasis. At present, there is no study to clarify the correlation between the primary location of the tumor and the metastasis pattern in advanced NSCLC. So we conducted this study to explored the relationship between the tumor primary location and metastasis pattern in stage IV NSCLC. METHODS: A total of 19,295 eligible patients were identified from 2010 to 2012 in the SEER database. The main endpoint of our study was overall survival (OS). The survival curves were created by using the Kaplan–Meier method and compared by the usage of the Log Rank test. The clinical variable characteristics were compared by the chi-square test, and multivariate logistic regression analyses were used to evaluate the risk factors on metastasis patterns. All statistical P values were two-sided, and it was considered statistically significant when P ≤ 0.05. RESULTS: We found that different proportions of metastatic sites could be found in different tumor primary locations. In addition, the prognosis of lung metastasis was relatively good in patients with tumor location in main bronchus (P < 0.001), upper lobe (P < 0.001), lower lobe (P < 0.001) , and middle lobe (P = 0.005). Besides, there was no significant OS difference for patients whose primary location was overlapping lesion (P = 0.226). The results also demonstrated that compared with patients with primary tumor located in the main bronchus, those in the upper lobe were more likely to have brain metastasis (P = 0.01) and lung metastasis (P = 0.024), those in the middle lobe were more prone to develop lung metastasis (P = 0.035) and those in the lower lobe were more apt to cause bone metastasis (P = 0.005) and lung metastasis (P = 0.001). In addition, there was no statistical difference in metastasis patterns among patients with overlapping lesions (P > 0.05). CONCLUSIONS: Different primary tumor locations might affect the metastasis pattern in patients with stage IV NSCLC.