Microscopic Venous Invasion in Pancreatic Cancer

Microscopic venous invasion (MVI) and the subsequent peripheral blood circulation of cancer cells are considered to be the primary route for systemic dissemination of pancreatic cancer. Patients who underwent pancreatectomy for invasive ductal carcinoma of the pancreas between January 2007 and December 2015 were retrospectively reviewed. The prognostic significance of MVI was analyzed. A total of 352 patients underwent pancreatectomy for invasive ductal carcinoma of the pancreas. A pathologic examination showed MVI in 228 (64.5%) of the patients. The median survival time (MST) was 21 months for the patients with MVI and 58 months for those without MVI (p < 0.001). A multivariate analysis showed the following to be significant prognostic factors: non-administration of adjuvant chemotherapy [hazard ratio (HR) 2.37; p < 0.001], lymph node metastasis (HR 2.95; p = 0.001), CA19-9 value of 300 U/ml or higher (HR 1.70; p = 0.018), and MVI (HR 1.84; p = 0.011). The overall survival was clearly stratified into three groups; favorable (MST not reached in stage 1 or 2A without MVI; p = 0.867), moderate (30 months in stage 2A with MVI and 30 months in stage 2B without MVI; p = 0.528), and poor (19 months in stage 2B with MVI and 17 months in stage 4; p = 0.322). The differences between these three groups all were significant. Approximately two-thirds of patients with radiologically resectable pancreatic cancer had MVI and were considered to have potentially systemic disease. This study identified MVI as one of the significant factors for a poor prognosis and a valuable complement of tumor-node-metastasis staging.