Second primary invasive cutaneous melanomas in Queensland over 4 decades

Second primary invasive cutaneous melanomas (SPICMs) are common and pose an increased risk of death compared with single invasive melanoma only. Using data from the Queensland Oncology Repository, we investigated changes in the cumulative incidence of SPICMs for people diagnosed with a first primary invasive cutaneous melanoma between 1982 and 2022, with follow-up until December 31, 2023. Death due to any cause was treated as a competing risk. Among the 101,035 people in the study cohort, 9% (n = 9224) were diagnosed with a metachronous SPICM. Estimated 40-year cumulative incidence of SPICMs was 16.3% (95% confidence interval = 15.8-16.8%). Ten-year cumulative incidence was 4.9% between 1982 and 1991, 7.0% for 1992-2001, 7.9% for 2002-2011, and 7.3% between 2012 and 2022. After multivariable analysis, people first diagnosed between 2012 and 2022 were 23% more likely to subsequently be diagnosed with a SPICM within 10 years than those first diagnosed in 1982-1991 (subhazard ratio = 1.23, 95% confidence interval = 1.11-1.35), whereas the subhazard ratio was 1.38 (95% confidence interval = 1.26-1.52) for 2002-2011. These results provide evidence that the cumulative incidence of SPICM may have plateaued within a population having the highest rates of melanoma in the world, possibly owing to the impact of long-running sun safety campaigns in Australia combined with increased surveillance.