Primary tumor resection and lymph node dissection improve survival in de novo metastatic pancreatic ductal adenocarcinoma: an inverse probability of treatment weighting analysis

BACKGROUND: Primary tumor resection (PTR) and lymph node dissection (LND) may be performed occasionally in patients with de novo metastatic pancreatic ductal adenocarcinoma (mPDAC). However, the role of PTR and LND in such cases remains unclear. Thus, we aimed to test the effect of PTR and LND on overall survival (OS) and cancer-specific survival (CSS) in mPDAC patients. METHODS: Patients with de novo mPDAC were identified from the Surveillance Epidemiology and End Results (SEER) database (2010–2015). The inverse probability of treatment weighting (IPTW) method was used to minimize the selection bias. IPTW-adjusted Kaplan-Meier curves and Cox proportional hazards models were used to compare OS and CSS in different treatment groups. RESULTS: A total of 10,036 patients met the inclusion criteria. Of these patients, 275 (2.7%) underwent PTR, while 217 (2.2%) also underwent LND with a median of 16 nodes removed. In the IPTW-adjusted Kaplan-Meier analysis, the median OS was 13 versus 6 months (P<0.001) for the PTR and non-PTR groups, respectively, and 15 versus 5 months (P=0.007) for the LND and non-LND groups, respectively. In the IPTW-adjusted Cox regression analysis, PTR was independently associated with better OS [hazard ratio (HR) 0.483, 95% confidence interval (CI): 0.468–0.498, P<0.001], as was LND (HR 0.286, 95% CI: 0.228–0.358, P<0.001). Similar results were observed in the analysis of CSS. In the LND group, the extent of LND was not associated with either OS or CSS. CONCLUSIONS: PTR and LND were independent prognostic factors that prolonged OS and CSS in de novo mPDAC patients. These findings must be validated in prospective randomized studies.