Impact of resection margin status on survival in advanced N stage pancreatic cancer - a multi-institutional analysis.

BACKGROUND: The present study aimed to examine the impact of microscopically tumour-infiltrated resection margins (R1) in pancreatic ductal adenocarcinoma (PDAC) patients with advanced lymphonodular metastasis (pN1-pN2) on overall survival (OS). METHODS: This retrospective, multi-institutional analysis included patients undergoing surgical resection for PDAC at three tertiary university centres between 2005 and 2018. Subcohorts of patients with lymph node status pN0-N2 were stratified according to the histopathological resection status using Kaplan-Meier survival analysis. RESULTS: The OS of the entire cohort (n = 620) correlated inversely with the pN status (26 [pN0], 18 [pN1], 11.8 [pN2] months, P < 0.001) and R status (21.7 [R0], 12.5 [R1] months, P < 0.001). However, there was no statistically significant OS difference between R0 versus R1 in cases with advanced lymphonodular metastases: 19.6 months (95% CI: 17.4-20.9) versus 13.6 months (95% CI: 10.7-18.0) for pN1 stage and 13.7 months (95% CI: 10.7-18.9) versus 10.1 months (95% CI: 7.9-19.1) for pN2, respectively. Accordingly, N stage-dependent Cox regression analysis revealed that R status was a prognostic factor in pN0 cases only. Furthermore, there was no significant survival disadvantage for patients with R0 resection but circumferential resection margin invasion (≤ 1 mm; CRM+; 10.7 months) versus CRM-negative (13.7 months) cases in pN2 stages (P = 0.5). CONCLUSIONS: An R1 resection is not associated with worse OS in pN2 cases. If there is evidence of advanced lymph node metastasis and a re-resection due to an R1 situation (e.g. at venous or arterial vessels) may substantially increase the perioperative risk, margin clearance in order to reach local control might be avoided with respect to the OS.