Implications of Perineural Invasion on Disease Recurrence and Survival after Pancreatectomy for Pancreatic Head Ductal Adenocarcinoma

Objective: To describe PNI and to evaluate its impact on disease-free (DFS) and overall survival (OS) in patients with resected pancreatic ductal adenocarcinoma (PDAC). Summary of Background Data: Although PNI is a prognostic factor for survival in many GI cancers, there is limited knowledge regarding its impact on tumor recurrence, especially in "early stage disease" (PDAC ≤20 mm, R0/ N0 PDAC). Methods: This multicenter retrospective study included patients undergoing PDAC resection between 2009 and 2014. The association of PNI with DFS and OS was analyzed using Cox proportional-hazards models. Results: PNI was found in 87% of 778 patients included in the study, with lower rates in PDAC ≤ 20 mm (78.7%) and in R0/N0 tumors (70.6%). PNI rate did not differ between patients who underwent neoadjuvant therapy and upfront surgery (88% vs 84%, P = 0.08). Although not significant at multivariate analysis (P = 0.07), patients with PNI had worse DFS at univariate analysis (median DFS: 20 vs 15 months, P < 0.01). PNI was the only independent predictor of DFS in R0/N0 tumors (hazard ratio [HR]: 2.2) and in PDAC ≤ 20 mm (HR: 1.8). PNI was an independent predictor of OS in the entire cohort (27 vs 50 months, P = 0.01), together with G3 tumors, pN1 status, carbohydrate antigen (CA) 19.9 > 37 and pain. Conclusions: PNI represents a major determinant of tumor recurrence and patientsa' survival in pancreatic cancer. The role of PNI is particularly relevant in early stages, supporting the hypothesis that invasion of nerves by cancer cells has a driving role in pancreatic cancer progression.