The burden of malignant melanoma--lessons to be learned from Austria

Abstract

Aim of study: Incidence rates of melanoma, generated by cancer registries (CRs), are susceptible to reporting inconsistencies due to increasing decentralisation of diagnosis. We therefore independently assessed the burden of melanoma in Austria.

Methods: We collected histopathological reports on melanoma of all patients diagnosed in Austria in 2011. Demographic and clinical characteristics, histopathological tumour stages were assessed. Their regional distributions and incidence rates were analysed and compared with data of national and international CRs.

Results: A total of 5246 patients were diagnosed with 1951 in-situ and 3295 invasive melanomas in Austria in 2011 (population 8.4 million). Age, sex and anatomic distribution corresponded to findings in other European countries, however, the incidence of 25/100,000 (world age-standardised rate) for invasive melanomas was two-fold higher than published by the Austrian CR (12/100,000). Varying frequencies in diagnosing thin melanomas (≤1 mm; n = 4415) accounted exclusively for significant regional disparities, while advanced tumours (>1 mm; n = 761) were evenly distributed. Western Austria showed the highest rates (36/100,000). Patients from eastern Austria whose melanomas were diagnosed in laboratories in western Austria (n = 76) showed significantly higher proportions of in-situ lesions (n = 43; 57%) compared to those whose tumours were diagnosed in eastern Austria (n = 4014; in-situ = 1369; 34%) (p < 0.0001).

Conclusions: In Austria, the melanoma burden and its potential socio-economic implications are significantly underestimated. Similarities of incidences indicate this could affect other European countries with well-established CRs and compromise international comparability of data. Austrian regional disparities suggest overdiagnosis of thin melanomas due to the variability of pathologists' thresholds for the diagnosis of early stage tumours.

Keywords: Cancer registry; Epidemiology; Incidence rate; Melanoma; Overdiagnosis; Underreporting.