The Primary Tumor Surgery Prolongs the Medium Cancer Specific Survival in Metastatic Colorectal Cancer Patients with Initial Isolated Unresectable Lung Metastasis: A SEER-based Retrospective Study

Abstract Background: The efficiency of primary tumor surgery (PTS) to patients who are diagnosed as colorectal cancer (CRC) with initial isolated unresectable lung metastasis (URLM) is still on debates.Methods: 1580 patients are involved in this study eventually, data from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015. Chi-square (Χ2) test examines the categorical variables. Hazard ratio (HR) and 95% confidence interval (95% CI) are used as the estimation of risk for mortality in univariate and multivariate Cox regression. Propensity score match (PSM) simulates the random progress. Kaplan-Meier method outputs the medium cancer specific survival (mCSS) and delineates the survival curve.Results: After PSM, PTS prolongs the mCSS time in surgery group compared to no-surgery group (40 months vs. 14 months, HR=0.396, P<0.001), and raises the 3-year CSS rate (37% vs. 12%, P<0.001). Radiotherapy has further survival benefits in surgery group (49 months vs. 32 months, HR=0.434, P=0.001). Chemotherapy, radiotherapy, and no peritoneum metastasis have better mCSS (31 months, 33 months, 30months respectively). Multivariate Cox regression turns out that patients older than 75 (HR=1.869, P<0.001), with poor differentiation or undifferentiation pathological grade (HR=1.796, P<0.001), with peritoneum metastasis (HR=1.650, P<0.001) have higher risks of death, and PTS (HR=0.396, P<0.001), chemotherapy (HR=0.330, P<0.001) are favor prognostic factors in mCRC with URLM.Conclusion: This study affirms the effectiveness of primary tumor surgery in the colorectal cancer patients with initial isolated unresectable lung metastasis. More random clinical trials or real-world researches need to be implemented.