Comparative effectiveness of primary tumor resection in patients with stage III pancreatic adenocarcinoma

BACKGROUND: Previous studies comparing primary tumor resection (PTR) to palliative treatment for advanced-stage pancreatic ductal adenocarcinoma (PDA) were limited by strong selection bias. We used multiple methods to control for confounding and selection bias to estimate the effect of PTR on survival for late-stage PDA. METHODS: Surveillance, Epidemiology, and End Results (SEER) 18 registry database for 2004 through 2014 was retrieved for the present study. A total of 4322 patients with stage III (AJCC, 6th) PDA were included in this study. Propensity score matching (PSM) was performed to eliminate possible bias. In addition, instrumental variable (IV) analysis was utilized to adjust for both measured and unmeasured confounders. RESULTS: A total of 4322 patients with stage III PDA including 552 (12.8%) who underwent PTR, 3770 (87.2%) without PTR, were identified. In the multivariable cohort, a clear prognostic advantage of PTR was observed in overall survival (OS) (P < 0.001) and disease-specific survival (DSS) (P < 0.001) compared to patients after non-surgery therapy. In the PSM cohort, patients in PTR group showed a better OS and DSS (both P values < 0.001) compared to patients in non-surgery group. The survival benefit of PTR for stage III PDA was not observed in the two-stage residual inclusion (2SRI) model. Estimates based on this instrument indicated that patients treated with PTR had similar OS (P = 0.448) and DSS (P = 0.719). In IV analyses stratified by chemotherapy and tumor location, patients undergoing PTR had similar OS and DSS compared to patients in non-surgery group across all subgroups. CONCLUSIONS: Survival with PTR did not differ significantly from palliative treatment in marginal patients with stage III pancreatic adenocarcinoma. High-quality randomized trials are needed to validate these results. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12885-019-5966-9) contains supplementary material, which is available to authorized users.