Lymph Node Ratio Is a Reliable Prognostic Marker after Neoadjuvant Therapy and Pancreaticoduodenectomy for Pancreatic Cancer, but Does Not Predict the Utility of Adjuvant Therapy

Abstract

Introduction: The role of additional adjuvant chemotherapy(AT) after neoadjuvant chemotherapy(NAT) and surgical resection for pancreatic ductal adenocarcinoma(PDAC) remains unclear. Lymph node ratio(LNR), defined as number of positive nodes divided by total resected nodes, is a well-established prognostic indicator for PDAC. The objective of this analysis was to determine if LNR predicts survival benefit attained from receipt of AT following NAT and resection. Methods: Patients who underwent pancreaticoduodenectomy after NAT from 2006-2017 with pathologically node-positive PDAC were identified using the National Cancer Database. Patients with metastatic disease or unknown lymph node status were excluded. Patients were grouped as receiving NAT plus AT, or NAT only. LNR within node-positive groups were compared with a cutoff of 0.15. Five-year overall survival was determined by Kaplan-Meier analysis and multivariate(MV) Cox proportional hazards modeling. Results: A total of 1,182 patients were included: 623 with LNR=0.1-0.14 and 559 with LNR>=0.15. Median survival was higher among LNR=0.1-0.14 than with LNR>=0.15(28.8 vs 20.5mos, log-rank p<.001). 606 patients received NAT plus AT, and 576 received NAT only. For patients with LNR=0.1-0.14, receipt of additional AT was associated with improved median survival of 33.9mos compared to 27.3mos(log-rank p=0.050). For LNR>=0.15, receipt of additional AT was associated with improved median survival of 23.3mos vs 18.2mos(log-rank p=0.0024). MV analysis revealed similar survival benefit from AT, with hazard ratios of 0.807(95%CI 0.678-0.960, p=0.0156) for LNR=0.1-0.14 and 0.79(95%CI 0.669-0.942, p=0.0084) for LNR>=0.15. Conclusion: Although LNR is a reliable prognostic indicator for PDAC, it does not predict the utility of AT after receipt of NAT.