Predictors of subsequent primary melanoma: a case-control study

Patients with history of malignant melanoma (MM) are at risk of developing subsequent primary MM (SPM). Predictors of SPM may be helpful to identify patients at higher risk. The objective of the study is to investigate the phenotypic traits, indirect actinic exposure features and pathological variables associated with the risk of development of SPM. A ten-year retrospective case-control study was undertaken involving patients following MM excision who underwent regular video-dermoscopic examination at 4-6-month intervals for the first 5 years, followed by annual dermoscopic examination for the following five years. Patients with only one primary cutaneous MM were compared with those who developed at least one SPM. A total of 577 patients were included, 309 (53.6%) men and 268 (46.5%) women (mean age, 55 +/- 15 years), comprising 450 patients with single melanoma and 127 with at least one SPM. The median time span to the SPM was 30 (IQR 12-53) months. Compared to the first melanoma, SPM were thinner, mean Breslow 0.56 +/- 0.64 mm vs 1.37 +/- 1.83 mm (p < 0.001); in situ MM prevalence 12% vs 36% (p < 0.001). 36 % of the patients with SPM developed it in the anatomical site of the previous melanoma. At multivariate analysis, having numerous naevi (i.e. 10-50 nevi) OR = 2.88 (95% CI 1.32-6.28, previous dysplastic naevi excisions OR = 2.51 (95% CI 1.53-4.12), solar lentigo OR = 2.68 (95% CI 1.67-4.31) and actinic keratosis OR = 3.09 (95% CI 1.64-4.31) were associated with an increased risk of SPM. These features may identify persons at increased risk of developing SPM.