Evaluating COVID-19 Pandemic Impact on Melanoma Incidence and factors in Regions with Different Infection Control Strategies

INTRODUCTION: The COVID-19 pandemic significantly disrupted melanoma care worldwide, raising concerns about diagnosis and treatment delays. OBJECTIVES: To compare changes in incidence and prognostic factors of invasive cutaneous melanomas across two regions with contrasting COVID-19 infection control strategies. METHODS: A retrospective population-based registry study using the Swedish quality registry for cutaneous melanoma (SweMR) and the Cancer Council in Victoria, Australia was performed. Incident invasive melanomas diagnosed between 2013 and 2021 were used for trend analyses considering the long-term underlying trends and seasonality. Regression models were used for analyses of prognostic variables (Breslow thickness, ulceration, lymph node status), comparing the time periods, "before COVID" and "during COVID" (using 1 March 2020 as interruption point). RESULTS: In Victoria, melanoma diagnoses declined during COVID across all age groups, most notably among patients <50 years. Median Breslow thickness remained 0.7mm, but the distribution shifted significantly (p<0.001), with an 8% increase in geometric mean ratio (95% CI, 5%-12%). In Sweden, measures of thickness remained unchanged during COVID, but the odds of ulceration increased slightly (OR 1.09; 95% CI 1.01-1.19). Lymph node metastasis rates were stable in both regions. A significant immediate drop in overall incidence followed COVID-19 onset in both regions, primarily driven by thin melanomas. In Victoria, the lower incidence level persisted without a subsequent slope change. In contrast, the Swedish melanoma incidence gradually realigned with the pre-COVID trend after the initial level change. The immediate incidence drop was most prominent among older age groups in both regions. CONCLUSIONS: COVID-19 influenced melanoma incidence and prognostic features in both Sweden and Victoria. Reduced incidence of particularly thin melanomas and modest worsening of prognostic markers were observed. Victoria showed a more sustained impact, possibly reflecting the stricter and longer-lasting pandemic control measures.