Impact of margin status and lymphadenectomy on clinical outcomes in resected pancreatic adenocarcinoma: implications for adjuvant radiotherapy.

Background: Adjuvant chemoradiotherapy (CRT) in the treatment of pancreatic ductal adenocarcinoma (PDA) is controversial. Minimal data exists regarding the clinical significance of margin clearance distance and lymph node (LN) parameters, such as extent of dissection and LN ratio. We assessed the impact of these variables on clinical outcomes to more clearly define the subset of patients who may benefit from adjuvant radiotherapy (RT).

Methods: We identified 106 patients with resected stage 1-3 PDA from 2007-2013. Resection margins were categorized as positive (tumor at ink), ≤1, or >1 mm. LN evaluation included total number examined (NE), number of positive nodes (NP), ratio of NP to NE (NR), extent of dissection, and positive periportal LNs. The impact of these variables was assessed on disease-free survival (DFS) and overall survival (OS) using multivariate cox proportional hazards modeling.

Results: In patients receiving adjuvant chemotherapy (CT) alone, greater margin clearance led to improved DFS (P=0.0412, HR =0.51). Range of NE was 4-37, with a mean of 19. NE was not associated with DFS or OS, yet absolute NP of 5 or more was associated with a significantly worse DFS (P=0.005). Whereas periportal lymphadenectomy did not result in improved DFS or OS, patients with positive periportal LN had worse clinical outcomes (DFS, P=0.0052; OS, P=0.023). The use of adjuvant CRT was associated with improved OS (P=0.049; HR=0.29).

Conclusions: In patients receiving adjuvant CT alone, there was a clinically significant benefit to clearing the surgical margin beyond tumor at ink. Having ≥5 NP and positive periportal LN led to significantly worse clinical outcomes. The addition of adjuvant RT to CT in resected PDA improved OS. A comprehensive evaluation of resection margin distance and LN parameters may identify more patients at risk for locoregional failure who may benefit from adjuvant CRT.