Survival-anchored examined lymph node thresholds after resection for pancreatic body/tail ductal adenocarcinoma: a SEER-based cohort study with anatomical evidence synthesis

Abstract Introduction: The optimal examined lymph node (ELN) count after resection for pancreatic body/tail ductal adenocarcinoma (PDAC) remains uncertain. Guidelines recommend 12-15 nodes, but the value of higher thresholds is unclear. Method: SEER patients with pancreatic body/tail PDAC undergoing resection from 2000 to 2020 were analysed. Survival-anchored ELN thresholds were assessed using log-rank cut-point search, segmented Cox analysis, adjusted restricted cubic splines, and overlap-weighted restricted mean survival time (OW-RMST). A structured synthesis of 17 studies compared threshold attainment after conventional distal pancreatectomy (DP), radical antegrade modular pancreatosplenectomy (RAMPS), and posterior/artery-first approaches. Results: Among 5107 patients, 3630 deaths occurred (71.1%). Log-rank analysis identified ELN = 12 as the optimal binary cut-point; segmented Cox analysis identified ELN = 21 as a change point (bootstrap 95% CI 6.0-35.0). Adjusted splines showed a nonlinear inverse association between ELN and mortality, with attenuation beyond approximately 21 nodes. Each 5-node increase in ELN was associated with lower mortality (HR 0.964, 95% CI 0.949-0.980; P < 0.001). At 60 months, OW-RMST gains for ELN >= 12, >= 14, and >= 21 were 2.59, 2.31, and 2.60 months. Estimated probabilities of achieving ELN >= 21 were 16.5% after conventional DP, 40.0% after RAMPS, and 82.7% after posterior/artery-first approaches, with lowest certainty for the latter. Conclusion: ELN >= 12 is a minimum quality benchmark after resection for pancreatic body/tail PDAC, whereas approximately 21 nodes may be a higher-yield target. RAMPS may improve target attainment, but survival superiority remains unproven.