Peripancreatic Fat Invasion Is an Independent Predictor of Poor Outcome Following Pancreaticoduodenectomy for Pancreatic Ductal Adenocarcinoma

Background Following pancreaticoduodenectomy for pancreatic ductal adenocarcinoma (PDAC), identification of peripancreatic fat tumor invasion promotes a tumor to stage T3. We sought to understand better the impact of histological peripancreatic fat invasion on prognosis and site of recurrence in a cohort of patients with PDAC. Methods We analyzed the patient demographics, outcome, and recurrence data that had been prospectively collected in 189 consecutive PDAC undergoing potentially curative pancreaticoduodenectomy between 1996 and 2009. Pathological features were reassessed for all patients. Survival outcome was compared using Kaplan-Meier/Cox proportional hazards analysis. The primary site of recurrence was defined as either locoregional or distant metastases. Results The median survival of this PDAC cohort was 18.9 months (95% confidence interval (CI) 15.7-22.2). Histological peripancreatic fat invasion was evident in 51 (27%) patients and was associated with lymph node metastases (p=0.004) and larger tumor size (p=0.015). The presence of peripancreatic fat invasion was associated with reduced overall survival following resection (12.4 months [95% CI 9.9-15.0]) when compared to those patients with no evidence of fat invasion (22.6 months [95% CI 18.5-26.7]; p < 0.0001). By multivariate survival analysis, independent predictors of overall survival included tumor grade (p=0.002), lymph node involvement (p=0.025), resection margin status (p=0.003), venous invasion (p=0.045), and peripancreatic fat invasion (p=0.007). Invasion into the pancreatic fat was significantly associated with the primary site of recurrence being locoregional failure (p=0.002). Conclusions Peripancreatic fat invasion was identified as being an independent predictor of poor outcome following pancreaticoduodenectomy for PDAC. Additionally, the presence of peripancreatic fat invasion was associated with locoregional disease as the primary site of recurrence. This may have implications for the staging of PDAC and potentially require incorporation into future staging systems to improve outcome stratification