P43 IS THERE AN OPTIMAL DEFINITION FOR POSITIVE CIRCUMFERENTIAL RESECTION MARGIN IN LOCALLY ADVANCED OESOPHAGEAL CANCER?

Abstract

Abstract Aim The utility of Circumferential Resection Margin (CRM) status in predicting prognosis in oesophageal cancer remains controversial, with two different definitions of a positive CRM, one from the College of American Pathologists (CAP) (tumour at margin) and the other from the Royal College of Pathologists (RCP) (tumour within 1 mm)1-3. This study aimed to analyze the validity of these definitions in oesophageal tumours and explore the optimal cutoff value for CRM to predict survival. Background & Methods Patients who underwent curative radical oesophageal resection for locally advanced (>pT2) adenocarcinoma or squamous cell carcinoma of the oesophagus were selected from 2007 to 2016. Patients with positive longitudinal resection margins were excluded. CRM was histologically reassessed using an ocular micrometer. Overall survival (OS) and disease-free survival (DFS) were estimated with uni and multivariate analyses. Results From 860 resected patients, 283 fulfilling the inclusion criteria were selected. CRM was measured as follows: CRM=0mm (n=48), 0<CRM ≤1mm (n=123) and CRM>1mm (n=112). In univariate (figure 1) and multivariate analysis R1 resection, according to both definitions was significantly associated with poor OS (CAP: HR=2.26,p<0.001; RCP: HR=1.42,p=0.035). However only CAP definition accurately predicted DFS (CAP: HR=2.25,p<0.001; RCP: HR=1.28,p=0.094). When comparing the 3 CRM groups and taking 0 < CRM ≤1mm as reference, only CRM=0 predicted OS and DFS (p<0.001). A CRM cutoff at 0.1 mm was the best to predict OS and differed according to histology. Conclusion Among existing definitions of CRM, CAP definition was more accurate to predict prognosis and recurrence. New cutoffs are promising.