Time trends in the incidence of multiple primary melanomas in Australia.

Abstract

The incidence of first primary melanoma has increased in many countries, but less is known about the incidence of multiple primary melanomas. We investigated trends in the incidence of multiple primary melanomas over time in Australia, and whether the trends differed by sex, age, and anatomical site. We examined the cumulative frequency and age-standardised incidence rates of second and higher-order primary melanomas in a population-based Australian cohort from seven cancer registries, comprising 299,535 individuals diagnosed with a first primary invasive melanoma between 1982 and 2016, and 221,973 individuals in a subset with a first invasive or in situ melanoma. The age-standardised incidence rate of second primary invasive melanoma within 5 years of a first primary invasive melanoma increased for males from 4.7 (95% confidence interval (CI):3.3-6.1) per 1000 person-years in 1982-1986 to 9.7 (95% CI:8.3-11.1) per 1000 person-years in 2012-2016, and for females from 3.1 (95% CI:2.6-3.6) to 8.0 (95% CI:6.8-9.2) respectively. When in situ and invasive melanomas were considered together, the incidence rates surged from 7.0 (95% CI:5.0-8.9) to 29.5 (95% CI:18.0-41.0) per 1000 person-years for males and from 4.8 (95% CI:3.9-5.7) to 20.4 (95% CI:18.7-22.2) for females. Incidence trends over time were similar by sex and age-group but differed by anatomical site. Over three decades in Australia, age-standardised incidence rates for second primary melanoma approximately doubled for invasive melanoma and increased by four-fold when in situ melanomas were included. These findings highlight the need for strengthened prevention and early detection to manage this burden.