Reassessment of the clinical significance of portal-superior mesenteric vein invasion in borderline resectable pancreatic cancer.

Objective: The principal objective of this study is to clarify the prognostic significance of borderline resectable pancreatic cancer (BRPC). The second objective is to evaluate the prognostic impact of the depth of pathological venous invasion.

Methods: The study included 122 pancreatic cancer patients who underwent curative surgery. All computed tomography scans of the patients were retrospectively interpreted and classified according to the NCCN guidelines, version 1.2016, as resectable (-) or borderline resectable (+) in each arterial (BR-A) and venous (BR-PV) involvement.

Results: The overall survival (OS) rate was significantly higher in BR-A(-) patients (n = 94) than in BR-A(+) patients (n = 28) (P = 0.001), whereas there was no difference between BR-PV(-) (n = 101) and BR-PV(+) patients (n = 21) (P = 0.257). In a multivariate analysis, the independent predictors of OS included BR-A(+) (P = 0.002), lymph node metastasis (P = 0.008), pathological venous invasion (P = 0.003), and adjuvant chemotherapy (P = 0.001). Of 39 patients who underwent venous resection, no significant difference was observed between BR-PV(-) (n = 20) and BR-PV(+) patients (n = 19) in resection rate, lymph node metastasis, the presence of extrapancreatic nerve invasion, recurrence rate, frequency of initial recurrence at a liver or local site, and OS. Pathological venous invasion was significantly deeper in BR-PV(+) patients. However, the depth of invasion was not associated with OS.

Conclusion: The definition of venous involvement in the current guidelines predicted the depth of pathological venous invasion but not OS in BRPC patients. Further prospective, randomized studies are needed to establish treatment strategies for BRPC patients with isolated venous involvement.