The Association Between Neoadjuvant Therapy and Pathological Outcomes in Pancreatic Cancer Patients After Resection: Prognostic Significance of Microscopic Venous Invasion

Background The impact of neoadjuvant therapy (NAT) on pathological outcomes, including microscopic venous invasion (MVI), remains unclear in pancreatic cancer. Methods A total of 456 patients who underwent pancreatectomy for resectable and borderline resectable pancreatic cancer between July 2012 and February 2020 were retrospectively reviewed. Patients were divided into two groups: patients with NAT (n = 120, 26%) and those without NAT (n = 336, 74%). Clinicopathological factors, survival outcomes and recurrence patterns were analyzed. Results Regarding pathological findings, the proportion of MVI was significantly lower in patients with NAT than in those without NAT (43% vs 62%, P = 0.001). The 5-year survival rate in patients with NAT was significantly better than that in those without NAT (54% vs 45%, P = 0.030). A multivariate analysis showed that MVI was an independent prognostic factor for the overall survival (OS) (hazard ratio 2.86, P = 0.003) in patients who underwent NAT. MVI was an independent risk factor for liver recurrence (odds ratio [OR] 2.38, P = 0.016) and multiple-site recurrence (OR 1.92, P = 0.027) according to a multivariate analysis. The OS in patients with liver recurrence was significantly worse than that in patients with other recurrence patterns (vs lymph node, P = 0.047; vs local, P < 0.001; vs lung, P < 0.001). The absence of NAT was a significant risk factor for MVI (OR 1.93, P = 0.007). Conclusion MVI was a crucial prognostic factor associated with liver and multiple-site recurrence in pancreatic cancer patients with NAT. MVI may be reduced by NAT, which may contribute to the improvement of survival in pancreatic cancer patients.