Classification of R1 resections for pancreatic cancer: the prognostic relevance of tumour involvement within 1 mm of a resection margin

Aims: The current Royal College of Pathologists guidelines for pancreatoduodenectomy specimen reporting recommend that microscopic evidence of tumour within 1 mm of a resection margin (RM) should be classified as R1. No clinical evidence exists to justify this classification. The aim of this study was to identify the proportion of pancreatoduodenectomy specimens in which 'equivocal' RMs are present (tumour involvement within 1 mm of, but not directly reaching, one or more resection margins) and whether the survival of these patients was similar to that of patients with 'unequivocal' RM involvement. Methods and results: Patients with histologically confirmed pancreatic ductal adenocarcinoma undergoing pancreatoduodenectomy between 1997 and 2007 (n = 163) were identified from a prospective database. One hundred and twenty-eight cases (79%) were classified as R1. Of these, 57 (45% of all R1 cases) were based on 'equivocal' margin involvement. There was no significant difference in overall survival between equivocal and unequivocal R1 resections (log rank, P = 0.102). All R1 resections had a poorer survival on univariate (log rank, P = 0.013), but not multivariate, analysis (Cox, P = 0.132). Conclusions: Our results indicate that cases with microscopic tumour involvement within 1 mm of a resection margin should be considered synonymous with incomplete excision for resected pancreatic cancer.