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5 Summary
Background:
The incidence of cutaneous melanoma (CM) has steadily increased over the past 50 years in predominantly fair-skinned populations. The observed increase is largely attributed to increasing risk exposure (UV radiation) and to demographic changes. While rates in Northern America and Oceania seem to have leveled off in recent years, particularly in younger cohorts, melanoma rates in most European countries continue to rise. The continual increase in incidence rates in higher age groups and their growing presence in the population will lead to a further sharp increase in the number of melanoma cases in the future. Estimating melanoma incidence trends and identifying the main forces (risk exposure and demographic changes) that might drive these trends are crucial for targeted cancer control measures aimed to reduce future melanoma burden.
Objectives:
To investigate the impact of UVR exposure and demographic changes on past/present incidence trends of CM and to estimate the future melanoma burden according to these changes for Germany and Denmark.
Material and Methods:
Melanoma incidence data (ICD-10, C43) for Germany (1995-2013) and Denmark (1943-2013) were retrieved from the Center for Cancer Registry Data (CCRD) at the Robert Koch-Institute and from the NORDCAN database. Historical (1980-2013) and projected population data (2014-2033) were sourced from national statistics agencies. Incidence trends (Germany: 1995-2013; Denmark: 1944-2013 and 1980-2013) were analyzed using joinpoint regression and quantified by calculating the estimated annual percentage change (EAPC) and its 95% confidence intervals. The number of future melanoma cases and incidence rates (2014/2018-2029/2033) were projected using modified age-period-cohort models. The increase in the number of melanoma cases was apportioned into contribution from change in population risk (UVR exposure) and changes in population size and age structure (demographic component). The numbers of melanomas attributable to high ambient levels of UV radiation at baseline (Germany: 1995/1998; Denmark: 1980/1983) were calculated by comparing baseline incidence rates (IRs) with those of a historical Danish cohort (1943/1947), minimally exposed to UVR. The analyses were carried out for age-standardized (ASIR) (European Standard Population, WHO 1976), crude (CIR) and age-specific (<40 yrs, 40-59 yrs, 60-79 yrs, 80+ yrs) incidence rates, recorded as 100,000 persons per year and stratified by sex.
Results:
The incidence of CM in Germany and Denmark has steadily increased during the past and will continue to do so for the foreseeable future. Between 1995/1998 and 2009/2013, the ASIRs in Germany almost doubled to 19.7/100,000 for men and to 19.4/100,000 for women. In Denmark, ASIRs increased for both sexes from less than 2 cases per 100,000 in 1944/1948 to 29.8 for men and to 34.3/100,000 per year for women in 2009/2013. IRs increased in all age groups. Sharp increases were noted for those aged 60+, particularly among men. Until 2029/2033, ASIRs in Germany will climb to ≥30 cases/100,000 (men: 29.9; women: 33.6). ASIRs in men will probably stabilize from 2024/2028 onwards. In Denmark, the ASIRs will reach 53.6 cases for males and 74.6 cases/100,000 for females. Stronger increases, without a leveling off, are expected for the CIRs and for those aged 60+ yrs, particularly for men. While IRs in people under 60 will stabilize or decline from the mid 2020s onwards in Germany, IRs in age groups ≤60 yrs will continue to rise in Denmark. Steeply rising IRs in higher age groups and population aging will significantly increase the number of melanoma cases in future. Until 2029/2033, their number will reach about 40,000 (men: 20,161; women: 19,397) in Germany and about 4,500 (men: 2,015; women: 2,484) in Denmark. Strong increases among those aged 60+ yrs, most evident among men (80+ yrs: Germany, 1995/1998-2029/2033: +1,140%; Denmark, 1980/1983-2029/2033: +3,627%) will change the age distribution of melanoma patients towards higher proportion of old and very old patients. In Germany, the number of patients aged 60+ yrs will rise from less than 50% (for both sexes) in 1995/1998 to 77% for men and to 61% for women in 2029/2033. In Denmark, their proportion will increase to around 70% for males and to 50% for females. Nevertheless, the contribution of demographic aging to the increase in melanoma cases at population level will be rather small (5-11% for men and about 5% for women for the period 2009/2013-2029/2033). In both populations, most of the increase in number of melanoma cases will be attributable to increasing UVR exposure, particularly among women (Germany: 90-95%, Denmark: 76-97%). Overall, including the number of melanomas attributable to high ambient UVR level at baseline, the population attributable fraction (PAF) of melanomas caused by UVR exposure in Germany will range between 84-92% for women and between 87-89% for men. Corresponding estimates for Denmark are: 85-96% (women) and 85-95% (men).
Conclusion:
In both populations, melanoma burden will increase in future. Most of the expected increase (80-97%) in melanoma diagnoses will be attributable to increasing exposure to UVR rather than to demographic aging. Since UVR is the only known modifiable risk factor for melanoma, a large number of melanoma cases could be prevented by reducing exposure to UVR. In order to steam the future melanoma burden, primary prevention should remain the cornerstone of melanoma control efforts. To counter the effects of an aging population, secondary prevention will be another important component for future melanoma control. |
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