Chapter 2 24 Pathology All specimens were revised by a single pathologist trained as a total mesorectal excision pathologist, andwith particular expertise in evaluating recurrent rectal cancer specimens using theMandard classification.17 pCRwas defined as the absence of tumour residue (Mandard score 1). Margin status was classified as either microscopic (R1) or macroscopic (R2) tumour present in the resection margin, or a tumour-free resection margin (R0). Patients with a pCR were classified as R0, but were analysed as a separate group to determine differences from R0 resections with and without pCR in survival curves. Statistical analysis To compare individual variables, t tests and χ2 tests were used when appropriate. OS for resected patients was calculated as the time interval between the date of resection of the recurrence and the date of last follow-up or death. LRFS was calculated as the time interval between the date of recurrence resection and the date of histological or evident radiological presence of a local rerecurrence. MFS was calculated as the time interval between the date of recurrence resection and the date of histological or evident radiological presence of distantmetastasis. OS, LRFS andMFSwere estimated using the Kaplan–Meier method, with differences assessed with the log rank test. Statistical analysis was performed using SPSS® version 23 forWindows® (IBM, Armonk, NewYork, USA). Sample size calculationswere donewith Power and Precision™ release 4.1 2012 (Biostat, Englewood, New Jersey, USA).
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