Comparison of royal college of pathologists and college of american pathologists definition for positive margins in oral cavity squamous cell carcinoma

Background: Pathological margin assessment is an essential component of surgical management of oral cavity squamous cell carcinoma (OCSCC), however, in many studies, variable definitions of involved margins have been used. The purpose of the present study was to compare the prognostic ability of involved margins according to Royal College of Pathologists (RCPath) and College of American Pathologists (CAP) guidance. Methods: Retrospective study of 300 patients with previously untreated OCSCC undergoing definitive surgical management. Main specimen margin status was defined according to RCPath guidance and CAP guidance. “Final margin status”, incorporated the results of frozen sections and extra tumour bed resections. The prognostic impact of each margin definition was studied using univariate analysis, and in multivariate models including T-stage (AJCC 8th edition), nodal status (pN+), extranodal extension (ENE), and use of adjuvant radiotherapy. Results: Both RCPath and CAP positive margins were associated with local recurrence (LR), disease-specific survival (DSS), and overall survival (OS) on univariate analysis, while final margin status was associated with LR and DSS, but not OS. On multivariate analysis, only CAP positive main specimen margin status was independently associated with LR (odds ratio 2.44, 95% CI 1.37, 4.34), DSS (odds ratio 2.28, 95% CI 1.31, 3.82), and OS (odds ratio 1.59, 95% CI 1.04, 2.42). Conclusions: Involved main specimen margin as defined by CAP guidance has the advantage of being an independent prognosticator of LR and survival in our cohort.