Introduction : Achieving microscopically clear resection (R0 resection) is the main goal of treatment. However, the definition of R0 resection, pathology reporting of pancreaticodudenectomy specimen are still no unified internationally. Thereby, margin status related with survival and recurrence is still controversial.

Methods : Patients who received curative resection for pancreatic head cancer in a single institution between 2010 and 2017 were enrolled. We compared survival and recurrence between R0 resection and R1 resection in two different definitions, 0mm R1 as direct margin involvement and 1mm R1 as resection margin less than 1mm. We classified to 4 groups by direction of pancreas ; pancreas transection, anterior surface, posterior and vessel margin.

Results : Total 314 patients were included, 0mm R1 rate was 15.6% and 1mm R1 rate was 36.3%. The 5-year survival rate was 23.1% in 0mm R0 group and 17.8% in 0mm R1 group, 25.4% in 1mm R0 group and 16.5% in 1mm R1 group. There was significant difference in 1mm R0/R1 status, however in 0mm R0/R1 status only tendency was found. In analysis of each margin, posterior margin involvement was related with OS and DFS in both definition. In multivariate analysis, preoperative CA 19-9 level, lymph node involvement, differentiation, angiolymphatic, venous invasion, postoperative radiotherapy status and 1mm posterior margin involvement were the independent risk factors of DFS.

Conclusions : Accurate standardized margin evaluation is crucial in pancreaticoduodenectomy specimen. 1mm definition of R1 is more beneficial for predicting survival. Active adjuvant treatments is suggested when posterior margin is involved.