Background Current literature recognises margins greater than 5mm as clear, in oral cavity squamous cell carcinoma (OCSCC). Margins less than 1mm and involved margins are indications for post-operative radiotherapy. There is a grey area with ‘close’ margins 1 to 4.9mm. We aim to evaluate survival and recurrence outcomes in those with clear margins, compared to those with involved, narrow <1mm and close 1 to 4.9mm margins. We further aim to explore whether there is a specific margin size within the 1-4.9mm range which significantly impacts survival and recurrence outcomes. We also aim to identify if there are predictive factors for presence of positive margins.
Methods All patients with OCSCC undergoing major head and neck surgery between 2009-2021 at Hutt Hospital have been identified from our Head and Neck Database. Primary outcome measures include overall survival (OS), cancer-specific survival (CSS), and recurrence-free survival (RFS). Univariate analysis will be performed OS, CSS and RFS in those with involved, <1mm and 1-4.9mm margins compared to those with clear >5mm margins. Multivariate analysis will be performed to adjust for confounding factors including patient demographics such as age, comorbidities, ethnicity, smoking status, alcohol intake, immunosuppression, gender and adjuvant post-operative radiotherapy, and tumour features including tumour stage, degree of differentiation, perineural invasion, lymphovascular invasion and metastatic disease. Our secondary aim is to identify whether there is a specific margin cut-off of significance in those with margins between 1 to 4.9mm compared to those with clear margins, and this will be done by comparing those with 1-1.9mm, 2-2.9mm, 3-3.9mm and 4-4.9mm margins to those with >5mm margins, to see whether a narrower margin may be associated with comparable outcomes. We will then evaluate the cohort of patients with positive margins and look at patient features and tumour features which may increase risk of having positive margins.