clinical characteristics and prognostic factors of lung adenosquamous carcinoma 
in seer database between 2010 and 2015

Background and objective The incidence and the mortality of lung cancer rank first among all malignant tumors and it seriously affects human health. The common types of non-small cell lung cancer (NSCLC) are adenocarcinoma and squamous carcinoma with clinical research and more attention, while adenosquamous carcinoma is a rare pathological subtype of lung cancer, which clinical features and prognostic factors are not yet fully understood. The purpose of this study is to analyze the clinical features and prognosis of lung adenosquamous carcinoma, and construct a nomogram to predict the patients’ prognosis. Methods We obtained the data of adenosquamous carcinoma patients diagnosed between 2010 and 2015 in the Surveillance, Epidemiology, and End Results (SEER) database of the United States, and compared their clinical features and prognosis with those of lung adenocarcinoma and lung squamous cell carcinoma patients in the same period. Then we used univariate and multivariate analyses to explore the independent prognostic factors of adenosquamous carcinoma. Finally, we constructed and validated a nomogram to visually predict the outcomes of lung adenosquamous carcinoma. Results 1,453 patients with lung adenosquamous carcinoma were finally included. Compared with patients with lung adenocarcinoma and lung squamous cell carcinoma, the distributions of lung adenocarcinoma patients in most of the variables were medium between lung adenocarcinoma and squamous cell carcinoma. The prognosis of adenosquamous carcinoma was better than that of lung squamous cell carcinoma, but worse than that of lung adenocarcinoma. Multivariate analysis showed that age, differentiation, tumor-node-metastasis (TNM), surgery, and chemotherapy were independent prognostic factors (all P were less than 0.001). We constructed a nomogram with a C-index of 0.783 (0.767-0.799). The distinction test and consistency test showed that the nomogram could predict the patient's prognosis effectively. Conclusion Lung adenosquamous carcinoma has unique clinical, pathological, and prognostic characteristics. Age, differentiation, T, N, M, surgery, and chemotherapy status are independent predictors of prognosis in patients with adenosquamous carcinoma. Our nomogram can efficiently predict the prognosis of patients.