The impact of margin status determined by the one-millimeter rule on tumor recurrence and survival following pancreaticoduodenectomy for pancreatic ductal adenocarcinoma

Purpose: The tumor-node-metastasis (TNM) classification defines R1 as the presence of tumor cells at the resection margin, while the current Royal College of Pathologists guidelines for pancreaticoduodenectomy specimens regard the presence of tumor cells within 1 mm from the resection margin as R1 (the "1-mm rule"). The aims of this study were to investigate the resection margin status of pancreatic head cancer retrospectively according to both the TNM and 1-mm rule classifications, and to evaluate the postoperative survival and tumor recurrence patterns. Methods: A total of 117 patients with pancreatic head cancer were the subjects of this study. Results: R1^1-mm rule resection was associated with a significantly worse disease-free survival (DFS) than R0^1-mm rule resection (p = 0.0259), while R1^TNM had no impact on DFS. R1^1-mm rule resection margin status correlated with the incidence of tumor recurrence in the liver (p = 0.0483). In a multivariate analysis, R1^1-mm rule resection was the independent variable for predicting poor DFS (hazard ratio 1.71; p = 0.0289). Conclusions: R1 resection margin status determined by the 1-mm rule may be an independent indicator for predicting disease recurrence, especially liver metastasis. These results may be useful for selecting the appropriate adjuvant therapy protocol and conducting strict surveillance in PDAC patients