Estimating the magnitude and healthcare costs of melanoma in situ and thin invasive melanoma overdiagnosis in Australia

Abstract Background Research suggests that a high proportion of melanoma in situ (MIS) may be overdiagnosed, potentially contributing to overtreatment, patient harm and inflated costs for individuals and healthcare systems. However, Australia-wide estimates of the magnitude of melanoma overdiagnosis are potentially outdated and there has been no estimation of the cost to the healthcare system. Objectives To estimate the magnitude and cost of overdiagnosed MIS and thin invasive melanomas in Australia. Methods Using two different methods to calculate lifetime risk, we used routinely collected national-level data to estimate overdiagnosed MIS and thin invasive melanomas (stage IA) in Australia in 2017 and 2021, separately for men and women. We multiplied the number of overdiagnosed melanomas by the estimated annual cost of a MIS or thin invasive melanoma, to quantify the financial burden of melanoma overdiagnosis to the Australian healthcare system in the year following diagnosis. Results We estimated that 67–70% of MIS were overdiagnosed in 2017, rising to 71–76% in 2021, contributing to between 19 829 95% confidence interval (CI) 19 553–20 105 and 20 811 (95% CI 20 528–21 094) cases of overdiagnosed MIS. In 2021, the estimated costs in Australia ranged between 17. 7 million Australian dollars (AUD; 95% CI 17. 4–17. 9 million) and AUD18. 6 million (95% CI 18. 3–18. 8 million). We estimated that 22–29% of thin invasive melanomas were overdiagnosed in 2017, rising to 28–34% in 2021, contributing to between 2831 (95% CI 2726–2935) and 3168 (95% CI 3058–3279) overdiagnosed thin invasive melanomas. In 2021, the estimated costs from thin invasive melanoma overdiagnoses ranged between AUD2. 5 million (95% CI 2. 4–2. 6 million) and AUD2. 8 million (95% CI 2. 7–2. 9 million). Conclusions Melanoma overdiagnosis is a growing clinical and public health problem in Australia, producing significant economic costs in the year following overdiagnosis. Limiting melanoma overdiagnosis may prevent unnecessary healthcare resource use and improve financial sustainability within the Australian healthcare system.