Cutaneous squamous cell carcinoma: predictors of positive and close margins and outcomes of re-excision in Northland, New Zealand.

BACKGROUND Non-melanoma skin cancer (NMSC) is the most commonly diagnosed and costly cancer in Australasia. Cutaneous squamous cell carcinoma (cSCC) accounts for approximately 25% of NMSC. A better understanding of predictors of close and positive margins following surgical excision will help guide treatment. METHODS A retrospective study was carried out of all primary cSCC histologically diagnosed in Northland, New Zealand in 2015. The cohort was identified by searching the regional pathology database. The primary outcome of interest was positive and close (≤1mm) margin rate following surgical excision and factors influencing them. Secondary outcomes of interest were outcomes of re-excisions. RESULTS A total of 1,040 cSCC were identified in 890 unique patients and 825 lesions were surgically excised. Increased odds of positive margin on surgical excision was found with increased tumour thickness (OR 1.56, 95% CI 1.24-1.96), tumours from the head and neck (OR 2.78, 95% CI 1.33-5.80) and those excised in primary care (OR 2.20, 95% CI 1.07-4.52). Increased odds of close margins was found in females (OR 2.01, 95% CI 1.3-3.2) and excision in primary care (OR 2.44 95% CI 1.5-3.98). Residual tumour was present in 13 (31.7%) patients with positive margins and 0 patients with close margins. CONCLUSIONS Lesions of the head and neck, those removed in primary care and with increased tumour thickness were more likely to have positive margins following surgical excision. Close margins were associated with excision in primary care and female gender. The value of re-excising tumours with close margins remains uncertain.