Objective: To investigate the impact of a surveillance program aimed at early diagnosis of melanoma in a cohort of subjects classified at risk on the basis of their number of nevi. To compare the number of observed cases of melanoma in the cohort to that expected number in the general population of the same area.
Methods: Two hundred and eighteen subjects with no personal or family history of melanoma residing in the Florence district who showed more than 30 common acquired nevi and 3 or more atypical nevi (high-risk) have been followed for an average period of 3.4 years (range 1-6.5); an additional intermediate-risk group with 237 subjects was also enrolled.
Results: Four incident melanomas were detected in 218 high-risk subjects followed for a total of 741.7 person-years; no melanoma was detected in the lower risk group. All the 4 detected melanomas were in situ (Clark level I), with an average interval since enrollment of 4.6 years (range 1.4-6.5). In accordance with age-and sex-specific incidence rates of melanoma (including in situ forms) in the general population of the area, the standardized incidence ratio (SIR) in the cohort was 44.1 (95% CI 16.5-117.5).
Conclusions: Subjects with more than 30 common nevi and 3 or more atypical nevi show about a 40-fold increased risk of developing melanoma. Even allowing for some degree of diagnostic anticipation due to periodic controls the risk appears higher than in the intermediate risk population. As a consequence of active follow up of individuals, all the detected tumors were at favourable prognosis. Periodic examination of these subjects should therefore be recommended as part of a prevention program for cutaneous melanoma in southern European populations.