AbstractBackgroundMajor vessel invasion is an important factor for determining the surgical approach and long-term prognosis for patients with pancreatic head cancer. However, clinical implications of vessel invasion have seldom been reported in pancreatic body or tail cancer. This study aimed to evaluate the clinical relevance of splenic vessel invasion with pancreatic body or tail cancer compared with no invasion and investigate prognostic factors.MethodsThis study enrolled patients who underwent upfront distal pancreatectomy from 2005 to 2018. The circular degree of splenic vessel invasion was investigated and categorized into three groups (group 1, no invasion; group 2, 0–180°; group 3, 180° or more). Clinicopathological variables and perioperative and survival outcomes were evaluated, and multivariable Cox proportional analysis was performed to evaluate prognostic factors.ResultsAmong 249 enrolled patients, tumour size was larger in patients with splenic vessel invasion (3.9 versus 2.9 cm, P = 0.001), but the number of metastatic lymph nodes was comparable to that in patients with no vessel invasion (1.7 versus 1.4, P = 0.241). The 5-year overall survival rates differed significantly between the three groups (group 1, 38.4 per cent; group 2, 16.8 per cent; group 3, 9.7 per cent, P < 0.001). Patients with both splenic artery and vein invasion had lower 5-year overall survival rates than those with one vessel (7.5 versus 20.2 per cent, P = 0.021). Cox proportional analysis revealed adjuvant treatment, R0 resection and splenic artery invasion as independent prognostic factors for adverse outcomes in pancreatic body or tail cancer.ConclusionSplenic vessel invasion was associated with higher recurrence and lower overall survival in pancreatic body or tail cancers suggesting a need for a neoadjuvant approach.