Surgical resection of a primary tumor improves survival of metastatic pancreatic cancer: a population-based study

Introduction: Pancreatic cancer is a lethal disease with a very poor prognosis. This study investigates survival of patients diagnosed with metastatic pancreatic cancer (mPC) based on local treatment of the primary tumor. Methods: Patients diagnosed with stage IV mPC between 2004 and 2013 were identified from the Surveillance, Epidemiology and End Results (SEER) database. Cancer-specific survival (CSS) and overall survival (OS) were examined. CSS and OS were examined by using the Kaplan-Meier method with the log-rank test. Multivariable survival analyses of CSS and OS were conducted using the Cox proportional hazard model. Results: A total of 28918 patients with mPC were included in this analysis. There were 467 patients who received surgical resection (1.6%) and 28451 patients who did not (98.4%). Patients who were younger than 70 years (odds ratio [OR]=1.45, 95% CI=1.04-2.03, p=0.03), diagnosed from 2004 to 2008 (OR=1.49, 95% CI=1.25-1.80, p<0.001), female (OR=1.31, 95% CI=1.08-1.58, p<0.001), married (OR=1.56, 95% CI=1.27-1.90, p<0.001), at T3 stage (OR=3.53, 95% CI=1.10-11.37, p=0.035), at N1 stage (OR=2.05, 95% CI=1.68-2.50, p<0.001), presenting histological types other than adenocarcinoma (OR=2.04, 95% CI=1.43-2.94, p<0.001), and with tumor of the pancreatic head (OR=1.90, 95% CI=1.27-2.82, p=0.002) were more likely to be treated with surgical resection. The results of multivariate analysis showed that surgical resection of the primary tumor was associated with CSS (hazard ratio [HR]=0.58, 95% CI=0.52-0.64, p<0.001) and OS (HR=0.59, 95% CI=0.53-0.65, p<0.001) benefits. In addition, not receiving chemotherapy (HR=2.33, 95% CI=2.27-2.39, p<0.001), age >50 years (HR=1.25, 95% CI=1.09-1.42, p=0.001), male (HR=1.121, 95% CI=1.09-1.15, p<0.001), black ethnicity (HR=1.11, 95% CI=1.1-1.15, p<0.001), unmarried (HR=1.20, 95% CI=1.17-1.23, p<0.001), histological type of adenocarcinoma (HR=1.18, 95% CI=1.14-1.22, p<0.001), and primary site other than the pancreatic head (HR=1.08, 95% CI=1.05-1.11, p<0.001) are factors associated with poor survival. Conclusion: This study reveals that local treatment has the primary benefit of both CSS and OS in patients with mPC. These results may guide the management of this patient population.National Natural Science Foundation of China [81672862]; Ministry of Education of China [20090001110096]; Capital Characteristic Clinical Application Research and Achievement Promotion Project [Z171100001017121]SCI(E)ARTICLE471-479