In pancreatic ductal adenocarcinoma, neural invasion is being increasingly recognized as an unfavorable predictor of patient outcomes. Neural invasion severity seems to have a stronger clinical impact on patient prognosis than neural invasion status alone. Therefore, this study aims to assess the impact of severity of neural invasion on overall survival and disease-free survival in pancreatic ductal adenocarcinoma. To assess the impact of intrapancreatic neural invasion severity, tumor specimens resected from patients with pancreatic ductal adenocarcinoma between 2007 and 2014 were systematically re-evaluated, and neural invasion severity was determined using the standardized neural invasion severity score. In our cohort (n= 216), an increased neural invasion severity score was associated with markedly shorter overall survival in pancreatic head ductal adenocarcinoma (neural invasion severity score low: 22.8months vs neural invasion severity score high: 17.6months: P= .001). An external European validation cohort confirmed these results and showed significantly better survival of patients with lower neural invasion (20.5 vs 15.4months, P= .026). The disease-free survival time was also substantially decreased in patients with pancreatic head pancreatic ductal adenocarcinoma and increased neural invasion severity (neural invasion severity score low: 19.1months vs neural invasion severity score high: 10.4months; P= .004). Moreover, the neural invasion severity score was an important independent factor influencing overall survival (hazards ratio 1.024, P= .04) and disease-free survival (hazards ratio 1.03, P= .01) using an adjusted Cox proportional hazards model. Importantly, higher neural invasion severity score leads to significantly more and earlier local recurrence than to distant tumor recurrence. Neural invasion severity is a powerful independent factor influencing overall survival and local recurrence in patients with pancreatic ductal adenocarcinoma. Therefore, individuals with high neural invasion severity score values should be regarded as a specific subgroup of pancreatic ductal adenocarcinoma patients and may benefit from more tailored postoperative oncologic therapy.
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