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Guoshu Bi,* Tao Lu,* Guangyu Yao, Yunyi Bian, Mengnan Zhao, Yiwei Huang, Yi Zhang, Liang Xue, Cheng Zhan, Hong Fan Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai 200032, People’s Republic of China*These authors contributed equally to this workCorrespondence: Hong Fan; Cheng ZhanZhongshan Hospital, No. 180 Fenglin Road, Xuhui District, Shanghai 200032, People’s Republic of ChinaTel +86 139 1689 7139Fax +86 21 6404 1990 Ext 2915Email fan.hong@zs-hospital.sh.cn; czhan10@fudan.edu.cnBackground: Lymph node ratio (LNR), defined as the ratio of the number of positive lymph nodes to the total of all resected nodes, has been reported to be a predictor of survival of patients with several types of cancer. However, the prognostic value of LNR and other factors in patients with resected N2 stage lung squamous cell carcinoma has never been considered.Methods: Data from 1778 patients with resected N2 stage lung squamous cell carcinoma were obtained from the Surveillance, Epidemiology, and End Results (SEER) database. The optimal cutoff value of LNR was identified by X-tile. A multivariable Cox model and corresponding nomogram were constructed to predict overall survival (OS) and cancer-specific survival (CSS). Both the cutoff value of LNR and the model were further validated in 146 similar patients treated in Zhongshan Hospital. Heat maps were created to visualize the distribution of LNR and the number of positive lymph nodes with the predicted survival probabilities.Results: The optimal cutoff value for LNR was identified as 0.42. Multivariable analysis showed that age, sex, tumor laterality, type of surgery, T stage, chemotherapy and LNR were independently correlated with OS. Harrell’s C-index of the nomogram (0.64) was significantly higher than the index of the T stage-based model (0.54). Calibration curves showed good agreement between predicted and observed survival probabilities. The robustness of the model was also demonstrated by external validation.Conclusion: LNR less than 0.42 was associated with improved OS and CSS for patients with resected N2 stage lung squamous cell carcinoma.Keywords: lymph node ratio, N2 stage lung squamous cell carcinoma, prognostic model, nomogram, heatmap

Tao Lu,* Xiaodong Yang,* Yiwei Huang, Mengnan Zhao, Ming Li, Ke Ma, Jiacheng Yin, Cheng Zhan, Qun WangDepartment of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, China*These authors contributed equally to this work Purpose: This study used the Surveillance, Epidemiology, and End Results (SEER) data to investigate the changes in incidence, treatment, and survival of lung cancer from 1973 to 2015.Patients and methods: The clinical and epidemiological data of patients with lung cancer were obtained from the SEER database. Joinpoint regression models were used to estimate the rate changes in lung cancer related to incidence, treatment, and survival.Results: From 1973 to 2015, the average incidence of lung cancer was 59.0/100,000 personyears. The incidence increased initially, reached a peak in 1992, and then gradually decreased. A higher incidence rate was observed in males than in females and in black patients than in other racial groups. Since 1985, adenocarcinoma became the most prevalent histopathological type.The surgical rate for lung cancer was about 25%, and treatment with chemotherapy showed an increasing trend, while the radiotherapy rate was in downward trend. The surgical rate for non-small-cell lung cancer (NSCLC) was higher than that for small cell lung cancer (SCLC), while chemotherapy for SCLC far exceeded that for NSCLC. Treatment with chemotherapy andradiotherapy for advanced stage had higher rate than early stage. The 5-year relative survival rate of lung cancer increased with time, but