Background: Current guidelines for the treatment of melanoma favour conservatism; however there is still uncertainty regarding best practice for lesions of intermediate thickness. Local recurrence, a measure of treatment adequacy, can be used to determine optimum excision margins and give prognostic information for survival.
Methods: An analysis of the Auckland Melanoma Unit database was performed. Patients with local recurrence were identified and stratified by lesion thickness. Optimum excision margins were derived by regression analysis and evaluated against the database population. Survival and prognostic factors were studied.
Results: Eighty-four of 1155 patients (7 per cent) developed local recurrence. Median follow-up was 51 months. Margins predicted to give a local recurrence of zero were: 1 cm for lesions < or = 1 mm thick; 1.5 cm for lesions 1-2 mm thick; and 2 cm for lesions > 2 mm thick. Applied to 1155 patients, there were significant differences in both local recurrence and mortality rates between optimally and suboptimally excised lesions, except for those > 4 mm thick. Thirty-three patients (39 per cent) with local recurrence died. Thickness, local recurrence and ulceration were of prognostic significance.
Conclusion: Development of local recurrence in melanomas < or = 4 mm thick is due to inadequate treatment. It signifies progressive disease and a poor prognosis. Care must be taken to ensure that all such lesions are optimally excised.