Histopathologic excision margin affects local recurrence rate: analysis of 2681 patients with melanomas < or =2 mm thick

OBJECTIVE: Prospective trials have shown that 1-cm and 2-cm margins are safe for melanomas <1 mm thick and > or =1 mm thick, respectively. It is unknown whether narrower margins increase the risk of LR or mortality. SUMMARY BACKGROUND DATA: To determine the relationship between histopathologic excision margin, local recurrence (LR) and survival for patients with melanomas < or =2 mm thick. METHODS: Data were extracted from the Sydney Melanoma Unit database for all patients with cutaneous melanoma < or =2 mm thick, diagnosed up to 1996. Patients with positive excision margins or follow-up <12 months were excluded, leaving 2681 for analysis. Outcome measures were LR (recurrence <5 cm from the excision scar), in-transit recurrence, and disease-specific survival. Factors predicting LR and overall survival were tested with Cox proportional hazards analysis. RESULTS: Median follow-up was 83.8 months. LR was identified in 55 patients (median time to recurrence, 37 months). At 120 months, the actuarial LR rate was 2.9%. Five-year survival after LR was 52.8%. In multivariate analysis, only margin of excision and tumor thickness were predictive of LR (both P = 0.003). When all patients with a margin <0.8 cm in fixed tissue (corresponding to a margin of <1 cm in vivo) were excluded from analysis, margin was no longer significant in predicting LR. Thickness, ulceration, and site were predictive of survival, but margin was not (P = 0.49). CONCLUSIONS: Histopathologic margin affects the risk of LR. However, if the in vivo margin is > or =1 cm, it no longer predicts risk of LR. Patient survival is not affected by margin.