Patient presentation, skin biopsy utilization and cutaneous malignant melanoma incidence and mortality in northern Italy: Trends and correlations

Background: The global increase in incidence of cutaneous malignant melanoma (CMM) occurring in the past decades has been partly attributed to increased diagnostic scrutiny of early lesions, with a potential phenomenon of overdiagnosis. The reported positive linear relation between skin biopsy rate and incidence of early CMM is compatible with this hypothesis. Objectives: We explored the ecological association between the trends in annual dermatologic office visit rates, skin biopsy rates, incidence rates of in situ and invasive CMM by tumour thickness category, and CMM mortality rates in the Emilia-Romagna Region (northern Italy). Methods: Four cancer registries covering a population of 2,696,000 provided CMM incidence data for the years 2003-2017. Dermatologic office visit rates and skin biopsy rates were calculated using the Regional outpatient care database. All rates were age-standardized. Trends were described with the estimated average annual per cent change (EAAPC). Correlations were tested with the Spearman correlation coefficient. Results: Incidence increased significantly. The increase was steeper for in situ CMM (EAAPC: men, 10.2; women, 6.9) followed by CMM <0.8 mm thick (9.1; 5.2), but the rates grew significantly for most subgroups of CMMs ≥0.8 mm thick. Mortality decreased significantly among women (-2.3) and non-significantly among men. For dermatologic office visit rate and skin biopsy rate the EAAPC were, respectively, 1.7 and 1.8 for men and 1.2 and 0.9 for women. Annual dermatologic office visit rate correlated with skin biopsy rate in both sexes. However, the proportion of skin biopsies out of dermatologic office visits was constant across the years (range: men, 0.182-0.216; women, 0.157-0.191). Conclusions: In Italy, the increasing CMM incidence trend is, at least in part, genuine. Overdiagnosis-if any-is due to an increased patient presentation at dermatologic offices and not to a lower dermatologic threshold to perform biopsy.