Significance of Portal Vein Invasion and Extent of Invasion in Patients Undergoing Pancreatoduodenectomy for Pancreatic Adenocarcinoma.

INTRODUCTION: Several studies have confirmed the safety of pancreatoduodenectomy with portal/mesenteric vein resection and reconstruction in select patients. The effect of vein invasion and extent of invasion on survival is less clear. The purpose of this study was to examine the association between tumor invasion of the portal/mesenteric vein and long-term survival.
METHODS: A retrospective review of a prospectively maintained database of patients who underwent pancreatoduodenectomy for pancreatic adenocarcinoma at a single academic medical center (2000-2014) was performed. Survival was compared using the Kaplan-Meier method and log-rank test. P < 0.05 was considered statistically significant.
RESULTS: After non-pancreatic periampullary adenocarcinomas and patients with non-segmental (lateral wall only) resection of portal/mesenteric vein were excluded, there were 567 eligible patients. Of these, segmental vein resection was performed in 90 (16 %) with end-to-end primary anastomosis (67) or interposition graft reconstruction (23). Patients with vein resection more likely received neoadjuvant systemic therapy (59 vs. 4 %, p < 0.0001). Histopathology of patients undergoing vein resection revealed a distribution of T stage toward larger tumors and higher rates of perineural invasion. Portal/mesenteric vein resection, however, was not associated with differences in hospital stay, postoperative complications, or operative mortality. Patients with or without vein resection had comparable overall survival rates at 1-, 3-, and 5-years. On final surgical histopathology, only 52 of 90 (58 %) vein resections had adenocarcinoma involvement of the venous wall. Of these, depth of invasion was at the level of the adventitia (9), media/intima (34), and full thickness/intraluminal (9). Venous wall invasion (52) did not significantly influence overall survival (14 vs. 21 months, p = 0.08) but was associated with significantly shorter median disease-free survival (11.3 vs. 15.8 months, p = 0.03), predominantly due to local recurrence. The extent of invasion (adventitia, media/intima, full thickness/intraluminal) did not impact overall survival or disease-free survival (14.4 vs. 15.5 vs. 7.4 months, p = 0.08 and 11.2 vs. 12.2 vs. 5 months, 0.59, respectively). Portal/mesenteric vein resection, histopathologic invasion, or the extent of invasion were not independent predictors of overall survival in Cox regression analysis.
CONCLUSION: Although Portal/mesenteric vein resection is associated with increased 90-day mortality, venous resection is not prognostic of overall survival. Although a subgroup analysis showed that a direct tumor invasion into the vein wall on final histopathology was associated with a higher rate of local recurrence but with no difference in overall survival (even when stratified according to extent of venous wall invasion), larger studies with an increased power will be needed to confirm these findings.