Incidence and Prognosis Nomogram of Small Solitary Lung Cancer (≤2 cm) With Extra-Thoracic Metastasis at Initial Diagnosis:A Population-Based Study

Background Small solitary lung cancer (≤2 cm) with extra-thoracic metastasis and no nodal metastasis or intra-thoracic metastasis is a rare situation in clinic. Methods Lung cancer patients with stage T1aN0M0 and T1aN0M1b from 2010 to 2015 were identified from the Surveillance, Epidemiology, and End Results database. The identified significant parameters were utilized to develop 2 nomogram to predict the extra-thoracic metastasis rates and the overall survival for the group of patients with stage T1aN0M1b. Results Small solitary lung cancers which occur in the males, younger patients, or locate in the main bronchus or left lung, or with histologic type as small cell lung cancer, or with undifferentiated type, tend to have extra-thoracic metastasis. Application of the nomogram in the intra-group still gave good discrimination and good calibration. Univariable and multivariable analysis identified several clinical data as the prognostic factors for lung cancer patients with stage T1aN0M1b, all the factors above were incorporated into the nomogram. ROC curve analysis showed that the nomogram had good discrimination, with AUC of .779, .786 and .77 for 1-, 3- and 5-year survival in the development group and validation group, respectively. Moreover, decision curve analysis has been implemented to evaluate and compare prediction and prognostic nomogram. Conclusions Younger male patients whose lung cancer locates in main bronchus or left lung, or with undifferentiated type, or with histologic type as small cell lung cancer are more likely to have extra-thoracic metastasis. The proposed nomogram reliably predicted OS for lung cancer patients with stage T1aN0M1b, though further validation is needed, it may be a useful tool in clinical practice. These models can be wildly used for easy facilitate the lung cancer individualized prediction of extra-thoracic metastasis and OS.