Differences in Uveal Melanoma Age-Standardized Incidence Rates in Two Eastern States of Australia Are Driven by Differences in Rurality and Ultraviolet Radiation

SIMPLE SUMMARY: Uveal melanoma (UM) is a rare form of melanoma originating in the eye. Unlike cutaneous melanoma (CM), the role of ultraviolet radiation (UVR) in UM aetiology is still unresolved. UM has a high incidence in Australia. Epidemiological analyses revealed heterogeneity in UM incidence between two eastern Australian states, Queensland (QLD) and Victoria (VIC). It was found that QLD has a 21% higher incidence of UM than VIC and, in fact, has one of the highest incidences in the world. A weak south-to-north trend in incidence along the eastern Australian coast is seen, and rural areas have a 24% greater burden than major city areas in both the states. The two states are similar demographically, but differ socially, industrially and latitudinally. This is important because it could indicate a minor UVR role in UM incidence, especially in QLD. Preventative measures by sun-protective behaviours may be important, especially in the northeastern Australian demographic. ABSTRACT: Uveal melanoma (UM) is the second-most-common melanoma in humans and has a high age-standardized incidence rate (ASR) in Australia. Regional patterns of UM ASRs in Australia are unknown. The aim of this study was to determine and compare UM ASRs in two geographically disparate eastern states, Queensland (QLD) and Victoria (VIC), by using cancer registry data that was obtained from 2001 to 2013. World-standardized UM ASRs and incidence-rate ratios (IRRs) were calculated. Higher UM ASR was also observed in anterior UM compared to posterior UM ASR. UM ASR remained unchanged from 2001 to 2013 in QLD but decreased in VIC. A south-to-north latitude trend in UM ASR along the east of Australia is weakly evident, and rural populations have higher UM ASRs than major city populations in both states. Differences in ultraviolent radiation (UVR) susceptibility, indigenous populations, social behaviours, chemical exposure, and socioeconomic status could all be contributing to differences in UM rates between QLD and VIC and between rural compared to major city areas. It is possible that a minority of cases in QLD and VIC might be prevented by sun-protective behaviours. This is important, because these findings suggest that QLD, which is already known to have one of the highest cutaneous melanoma (CM) ASRs in the world, also has one of the highest UM ASRs.