North-south differences in incidence and surveillance of cutaneous malignant melanoma in Italy

Background: In Italy, the incidence of cutaneous malignant melanoma is two-fold higher in the north than in the south. This gradient might be associated with differences in incidence trends and disease surveillance. We compared the time trends in incidence rates, mortality rates, dermatologic office visit rates and skin biopsy rates between the Emilia-Romagna Region (northern Italy) and the Sicily Region (southern Italy). Methods: The cancer registries of Parma, Modena, Ferrara and Romagna (current population, 2,606,465) and Catania-Messina-Enna, Siracusa and Ragusa (2,775,019) provided incidence and mortality records for the years 2008-2017. The records of outpatient services delivered in public health facilities were obtained from the two Regional Administrations. Trends in rates were assessed with the estimated average annual percent change. North-south differences were expressed as age-standardised rate ratios. Results: In the context of a generalised increasing incidence trend, which was more moderate in the female population of the Sicily Region, the standardised rate ratios were: 5.31 (males) and 5.20 (females) for in situ cutaneous malignant melanoma; 2.10 and 2.07 for invasive cutaneous malignant melanoma, with an excess incidence concentrated in lesions ⩽1.00 mm thick (3.58 and 3.05); 3.00 and 2.44 for dermatologic office visits; and 5.25 and 5.02 for skin biopsies. Mortality was stable in both Regions. Conclusions: In the Emilia-Romagna Region, as compared with the Sicily Region, a higher incidence of cutaneous malignant melanoma -especially of in situ and early invasive cutaneous malignant melanoma- coexisted with a higher level of clinical surveillance. The question of the direction of the cause-effect relationship between increased incidence and increased diagnostic scrutiny remains open.