Race-, Age-, and Anatomic Site-Specific Gender Differences in Cutaneous Melanoma Suggest Differential Mechanisms of Early- and Late-Onset Melanoma

Abstract

In order to explore melanoma risk factors through gender-, age-, race-, and site-specific incidence rates, malignant melanoma cases from the Caucasian whites and non-whites were retrieved from the US SEER database. Age-standardized, age-, and site-specific tumor rates were calculated. All races and both genders showed positive annual average percentage changes (AAPCs) over the years, but AAPCs varied at different body sites, with men's trunk exhibiting the fastest increase. Non-whites were diagnosed at a significantly younger age than whites and showed a trend towards fewer gender differences in the age of diagnosis. However, non-whites and whites showed a similar pattern of age-specific gender differences in the incidence rate ratios. A consistent spiked difference (female vs. male, incidence rate ratio (IRR) >2) was observed at or near the age of 20⁻24 in all race groups and at all body sites. The highest female vs. male IRR was found in the hip and lower extremities, and the lowest IRR was found in the head and neck region in all races. These race-, gender-, and site-dependent differences suggest that age-associated cumulative sun exposure weighs significantly more in late-onset melanomas, while genetics and/or pathophysiological factors make important contributions to early-onset melanomas.

Keywords: UV; anatomic body site; annual average percentage change; gender difference; incidence rate; incidence rate ratio; melanoma; non-white; race difference.

Figure 1

Melanoma incidence rates by age, sex, and anatomic site. (A–D) White population. (E–H) Non-white populations. (A,E) Head and neck area. (B,F) Upper limbs and shoulder area. (C,G) Trunk. (D,H) Lower limbs and hip area (SEER 18 data, 2000–2015).

Figure 2

The age-specific female to male incidence rate ratios by anatomic site. (A) White population. (B) Non-white populations, including black Americans, Hispanics, American Indians/Alaska Natives, and Asian Americans/Pacific Islanders (SEER 18 data, 2000–2015).

Figure 3

The trend of site-specific melanoma incidence rates by sex. (A) Incidence rates in the white population. (B) Average annual percentage change of site-specific incidence rates in each sex. (C) Overall female to male incidence rate ratios (SEER 9 data, 1973–2015). Left, white population. Right, non-white populations.