Prognostic impact of regression in patients with primary cutaneous melanoma >1 mm in thickness

Background: The impact of histologic regression on sentinel lymph node biopsy (SLNB) status and on clinical outcome is uncertain. Objective: To investigate whether and to what extent regression <75% is able to predict SLNB status and clinical outcome of patients with melanoma >1-mm thick. Methods: The study included patients with diagnoses given at 4 centers of the Italian Melanoma Intergroup. Univariate and multivariate Cox proportional hazard models stratified by center were used to analyze the effect of regression on disease-free interval and melanoma-specific survival. Results: Out of 1182 patients given primary cutaneous melanoma diagnoses during 1998-2015 with a Breslow thickness >1 mm, 954 (304 with and 650 without regression) were included in the analysis. The proportion of patients with a positive SLNB was lower in patients with regression than without (24.4% vs 31.6%, chi-squared test P =.0368). At multivariate analysis, no association was detected between regression and disease-free interval (hazard ratio 1.11, 95% confidence interval 0.85-1.46; P =.4509) or melanoma-specific survival (hazard ratio 1.05, 95% confidence interval 0.77-1.44; P =.7600). Limitation: Retrospective analysis. Conclusion: In our series, regression was not an independent prognostic factor in primary cutaneous melanoma patients with Breslow thickness >1 mm whereas it was associated with a lower incidence of SLNB positivity.