Prognostic Value of Perineural Invasion in Resected Gastric Cancer Patients According to Lauren Histotype.

The purpose of this study is to investigate perineural invasion (PNI) as a prognostic factor in gastric cancer patients. 455 patients submitted to extended (D2 or more) lymphadenectomy (median number of 39 retrieved lymph nodes, range: 15-140) between 1995 and 2012 were retrospectively studied. Patients were categorized in two groups according to the PNI status, and PNI positivity was assessed in presence of cancer cells in the perinerium or the neural fascicles using hematoxylin and eosin staining. Median follow-up for surviving patients was 80.3 months. Survival analysis was performed by univariate and multivariate analysis, using a Cox proportional hazards model. 162 patients (33.9%) had positive PNI; this was strongly associated with advanced stages of disease, residual tumor, lymphovascular invasion, Lauren diffuse-mixed histotype and tumor size. Five-year cancer-related survival was 65,7% and 20,6% in PNI negative vs. positive groups, respectively (p < 0.001). The prognostic impact of PNI at univariate analysis was particularly evident in patients submitted to R0 surgery, early as well as advanced stage, advanced nodal stage and T status. At multivariate analysis, PNI did not result statistically significant in the overall series, but emerged as an independent prognostic factor in the group of patients with Lauren intestinal histotype (p = 0.005, hazard ratio: 1.99, 95% confidence interval 1.24-3.19). PNI is related to advanced stage and poor long-term survival in gastric cancer, and may serve as an adjunctive prognostic factor in the intestinal histotype.