Abstract
IMPORTANCE: Men and women develop melanoma at different rates on different body sites, with variation across countries, but explanations for these disparities remain elusive. OBJECTIVE: To test whether observed differences in melanoma incidence between men and women vary by population, age, or anatomic site. DESIGN: Cross-sectional analysis of sex- and site-specific temporal trends in melanoma incidence over 3 decades was conducted for men and women diagnosed with invasive melanoma in the US (limited to white race), Canada, Australia, New Zealand, the UK, Sweden, Norway, and Denmark. Using cancer registry data, male to female incidence rate ratios (IRRs) were calculated overall and by anatomic site, and Joinpoint regression models were used to estimate the annual percentage rate changes in sex- and site-specific incidence in each population. Incidence rates were standardized to the US 2000 population. Data on the incidence between January 1, 1982, and December 31, 2015, were obtained; analysis was conducted from March 1 to October 15, 2019. MAIN OUTCOMES AND MEASURES: Male to female IRRs and annual percentage change in rates. RESULTS: Total melanoma incidence was higher in men than women in US individuals (limited to white race), Canada, Australia, and New Zealand, but not in Denmark, the UK, Norway, and Sweden. In all populations, men had higher rates of melanoma of the head and neck and trunk than women (male to female IRR >1), but lower melanoma rates on the lower limbs (ie, male to female IRR approximately 0.5). The male to female IRR increased log linearly with age, with excess melanomas in women younger than 45 years in all populations (eg, IRR for 20-24 y age group, 0.3 in Denmark and 0.7 in Australia), and excess melanomas in men older than 69 years (eg, IRR for 70-74 y age group, 1.1 in Denmark and 2.1 in the US white population). The age at which the melanoma incidence in men exceeded the melanoma incidence in women differed by population, being achieved the earliest in Australia (45-49 years) and latest in Denmark (65-69 years). CONCLUSIONS AND RELEVANCE: In predominantly fair-skinned populations, melanoma incidence appears to differ systematically and consistently between men and women by age and anatomic site.