Adenocarcinoma of the pancreas: Does prognosis depend on mode of lymph node invasion?

Background: Lymph node (LN) invasion in pancreatic ductal adenocarcinoma (PDAC) is the most important prognostic factor after surgical resection. The mechanisms of LN invasion include lymphatic spreading and/or direct extension from the main tumor. However, few studies have assessed the impact of these different patterns of invasion on prognosis.
Patients and Methods: Pathologic reports of pancreatic resections for PDAC from 1997 to 2007 were retrospectively analyzed. The mode of LN invasion was defined as follows: standard lymphatic metastases (S), contiguous from the main tumor (C) and standard with extracapsular invasion (EI). Clinical outcomes were compared according to the mode of invasion and the number of invaded LN.
Results: 306 patients were reviewed. Median age at resection was 61 years (range, 34-81). Eighty seven patients were N- (28.9%) and 214 were N+ (71.1%). Of the N+ patients, 195 (91.1%) were S+, 35 (16.3%) were C+, and 24 (12.3% of the S+ patients) were EI+. Median survival in N+ patients was lower than in N- patients (29 vs. 57 months, p < 0.001). In patients without standard involvement, C+ patients (n = 19) had worse survival than C- patients (n = 47) (34 vs. 57 months, p = 0.037). In S+ patients, C status was correlated with prognosis when the number of LN S+ was <2 (p = 0.07). EI status had no influence on prognosis. On multivariate analysis, only perineural invasion (p = 0.02) and LN ratio (p = 0.042) were independent prognostic factors.
Conclusion: Direct invasion of LN by the tumor is predictive of reduced survival, but has little impact compared to standard LN involvement and perineural invasion.
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