Does Sex Matter? Temporal Analyses of Melanoma Trends among Men and Women Suggest Etiologic Heterogeneity

The incidence and distribution of cutaneous melanoma differ between the sexes, but it is unclear whether these differences have been constant through time or across generations. We compared incidence trends by age, sex, and anatomic site by analyzing long-term melanoma data (1982-2018) in 3 populations residing at high-, moderate-, and low-ambient sun exposure: Queensland, Australia; United States White; and Scotland. We fit age- period- cohort models and compared trends in the male-to-female incidence rate ratio by site and sex. In men, melanoma incidence was always highest on the trunk; in women, incidence was historically highest on limbs, but there have been recent increases in truncal melanoma among females in all populations. The incidence rate ratio showed excess melanoma on the lower limb in females in most age groups in all populations. In contrast, there was a male excess of melanoma on the trunk (from about age 25 years) and head/ neck (from about age 40 years), which increased with age. Birth cohort analyses identified turning points in incidence from high to low incidence among recent birth cohorts, which differed by population and site. Changing exposure to UVR is implicated, possibly superimposed upon innate differences between the sexes in site-specific susceptibility.