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.