Divergent Melanoma Trajectories in the Western Pacific: Declining Mortality in Oceania and Diagnostic Challenges for Non-UV Subtypes in Asia

Introduction Melanoma exhibits substantial geographic heterogeneity in incidence, mortality, and subtype distribution. Independent population-based studies indicate that superficial spreading melanoma is more common in Oceania, whereas acral and mucosal melanomas constitute a larger proportion of melanoma in East and Southeast Asia, where epidemiological patterns differ substantially across countries and territories in the Western Pacific region. We aimed to characterize divergent melanoma incidence and mortality trajectories and quantify the demographic contributors to changes in absolute burden across the Western Pacific region from 1990 to 2021. Methods Data from the Global Burden of Disease Study 2021 for 28 Western Pacific countries and territories within the WHO Western Pacific Region with complete GBD 2021 melanoma estimates were analyzed overall and stratified into an Oceania subregion (Australia and New Zealand) and an Asian-predominant subregion comprising the remaining included countries in East and Southeast Asia. Joinpoint regression was used to estimate annual percent changes (APCs) and average annual percent changes (AAPCs) with 95% confidence intervals (CIs); hierarchical clustering was used to group countries according to incidence-mortality trajectories; Das Gupta decomposition was used to quantify the contributions of population growth, aging, and epidemiological change to changes in absolute case and death counts; and Nordpred was used to generate conditional projections to 2045 with 95% prediction intervals (PIs). All rates were age-standardized to the Global Burden of Disease standard. Results In Oceania, the population-weighted age-standardized incidence rate (ASIR) was 33.54 per 100,000 population, whereas age-standardized mortality rate (ASMR) declined (AAPC −1.28%, 95% CI: −1.70% to −0.86%). In the Asian-predominant subregion, the population-weighted ASIR was 0.58 per 100,000 population, but the ASMR increased (AAPC +0.39%, 95% CI: 0.36% to 0.42%). For incident cases, population growth and aging accounted for 53.9% and 34.1% of the net increase, respectively. For deaths, epidemiological change contributed −113.3% of the net increase, offsetting contributions from population growth and aging. The Republic of Korea had the largest increase in ASIR (AAPC 4.58%), whereas Australia had the largest decline in ASMR (AAPC −1.64%). By 2045, incident cases and deaths are projected to reach 201,744 (95% PI: 179,523 to 224,763) and 16,909 (95% PI: 14,357 to 19,868), respectively, under current trends. Conclusion The melanoma burden in the Western Pacific region shows two divergent epidemiological trajectories that are consistent with differences in subtype distribution and health-system context. Oceania’s experience indicates that UV protection and early detection may reduce mortality, whereas rising mortality in Asia underscores the need for improved recognition of acral and mucosal lesions and subtype-specific strategies. These findings support sociodemographic index (SDI)-stratified approaches that incorporate subtype-specific considerations into melanoma prevention, diagnosis, and health-system planning.