Abstract: Background and purpose: Small cell lung cancer (SCLC) is the most malignant pathological type of lung cancer, and is prone to distant metastasis. The site of metastasis and tumor burden can predict the prognosis. The purpose of this study was to compare impacts of the different sites of distant metastasis and the number of metastatic organs on the prognosis of extensive- stage SCLC patients to provide reference for clinical decision. Methods: Clinical data of extensive-stage SCLC patients from May 2014 to February 2019 in Shanghai Pulmonary Hospital, Tongji University were collected, and the relationship between the sites of distant metastasis / the number of metastatic organs and overall survival (OS)/therapeutic efficacy was retrospectively analyzed. Results: Most of patients (69.0%) had distant metastasis at the initial diagnosis. The greater the number of metastatic organs, the shorter the median OS (P=0.007 9) and progression-free survival (PFS) (P=0.027 0). The median OS of patients with brain metastasis, bone metastasis, contralateral lung metastasis, liver metastasis and other organ metastasis were 14.83, 11.70, 14.47, 11.10 and 12.47 months, respectively (P=0.031 1). The median PFS of patients with brain metastasis, bone metastasis, contralateral lung metastasis, liver metastasis and other organ metastasis were 5.07, 4.07, 7.10, 3.87 and 4.80 months, respectively (P=0.033 6). Conclusion: Distant metastasis in patients with extensive-stage SCLC suggests poor prognosis, and the more metastatic organs, the worse the OS and PFS. Patient with liver and bone metastases has worse OS and PFS suggesting poor prognosis.

Key words: Extensive-stage small cell lung cancer, Organ metastasis, Survival time