A unique gender difference in early onset melanoma implies that in addition to ultraviolet light exposure other causative factors are important

Abstract

Using US SEER17 Registry data, age-specific melanoma incidence rates were calculated and comparisons were made between males and females. Relative Risk (RR) for males and females in each age group was computed and compared with that from Nordic Cancer Registry data set and to that for non-melanoma skin cancer (NMSC). For age groups 44 and younger, females showed higher incidence rates, with a peak difference at age 20-24 (RR = 2.01, 95% CI = 1.21-3.33). Males exhibited higher incidence rates after age 44. The same bimodal gender difference was confirmed by the Nordic Cancer Registry data set, but it was not observed for NMSC, which is known to be strongly associated with cumulative exposure to solar UV radiation. We conclude that exposure to solar ultraviolet (UV) radiation is the major causative factor for melanoma at older age (>44 yr), but that other factors may play a role in early onset melanomas, particularly in females.

Figure 1

The study populations. (A) The gender and age distribution of SEER17 population from 1973 to 2008 (in personyears). (B) The gender and age distribution of Nordic population (1980–2006, in personyears).

Figure 2

The gender difference of melanoma in different age groups. (A) age-specific incidence rates (per 100 000 personyears) for males and females from US SEER17 data set. The figure inside is on a different scale. (B) Age-specific relative risks for females as compared to males. (C) normalized difference (ND = (IR_F−IR_M)/IR_T)) between male and female for each age group.

Figure 3

Detailed analysis of SEER17 data set for different years of diagnosis, histology subtypes, disease stages, body sites, geographic location, and ethnic groups. Normalized gender difference in incidence rates for (A), every 5-yr intervals from 1984 to 2008; (B) different disease stages; (C) different histology subtypes; (D) different body sites; (E) northern and southern areas; and (F) Caucasian and non-Caucasian groups.

Figure 4

The bimodal pattern was confirmed in Nordic population but not shown for Non-melanoma skin cancer. (A) age-specific melanoma incidence rates in the Nordic population for men and women (1980–2006). (B) The normalized gender difference in incidence rates in Nordic countries (1980–2006). (C) age-specific gender difference in NMSC in Nordic Cancer Registry. The figure within the panel is on a different scale showing subtle differences for younger age groups. (D) The normalized gender difference in incidence rates in NMSC in Nordic countries (1980–2006).

Figure 5

The bimodal etiology of melanoma. Melanomas in young population may have other causes than UV radiation while melanomas in older population may have a predominantly UV cause.