Thick melanoma in Tuscany

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.

The relative contribution of the decreasing trend in tumour thickness to the 2010s increase in net survival from cutaneous malignant melanoma in Italy: a population-based investigation

BACKGROUND

The long-term increase in survival from cutaneous malignant melanoma (CMM) is generally attributed to the decreasing trend in tumour thickness, the single most important prognostic factor.

OBJECTIVES

To determine the relative contribution of decreased tumour thickness to the favourable trend in survival from CMM in Italy.

METHODS

Eleven local cancer registries covering a population of 8 056 608 (13.4% of the Italian population in 2010) provided records for people with primary CMM registered between 2003 and 2017. Age-standardized 5-year net survival was calculated. Multivariate analysis of 5-year net survival was undertaken by calculating the relative excess risk (RER) of death. The relative contribution of the decrease in tumour thickness to the RER of death was evaluated using a forward stepwise flexible parametric survival model including the available prognostic factors.

RESULTS

Over the study period, tumour thickness was inversely associated with 5-year net survival and multivariate RER in both sexes. The median thickness was 0.90 mm in 2003-2007, 0.85 mm in 2008-2012 and 0.75 mm in 2013-2017 among male patients, and 0.78 mm, 0.77 mm and 0.68 mm among female patients, respectively. The 5-year net survival was 86.8%, 89.2% and 93.2% in male patients, and 91.4%, 92.0% and 93.4% in female patients, respectively. In 2013-2017, male patients exhibited the same survival as female patients despite having thicker lesions. For them, the increasing survival trend was more pronounced with increasing thickness, and the inclusion of thickness in the forward stepwise model made the RER in 2013-2017 vs. 2003-2007 increase from 0.64 [95% confidence interval (CI) 0.51-0.80] to 0.70 (95% CI 0.57-0.86). This indicates that the thickness trend accounted for less than 20% of the survival increase. For female patients, the results were not significant but, with multiple imputation of missing thickness values, the RER rose from 0.74 (95% CI 0.58-0.93) to 0.82 (95% CI 0.66-1.02) in 2013-2017.

CONCLUSIONS

For male patients in particular, decrease in tumour thickness accounted for a small part of the improvement in survival observed in 2013-2017. The introduction of targeted therapies and immune checkpoint inhibitors in 2013 is most likely to account for the remaining improvement.