Associations of cumulative sun exposure and phenotypic characteristics with histologic solar elastosis

Abstract

Background: Solar elastosis adjacent to melanomas in histologic sections is regarded as an indicator of sun exposure, although the associations of UV exposure and phenotype with solar elastosis are yet to be fully explored.

Methods: The study included 2,589 incident primary melanoma patients with assessment of histologic solar elastosis in the population-based Genes, Environment, and Melanoma study. Ambient erythemal UV (UVE) at places of residence and sun exposure hours, including body site-specific exposure, were collected. We examined the association of cumulative site-specific and non-site-specific sun exposure hours and ambient UVE with solar elastosis in multivariable models adjusted for age, sex, center, pigmentary characteristics, nevi, and, where relevant, body site.

Results: Solar elastosis was associated most strongly with site-specific UVE [odds ratio (OR) for top exposure quartile, 5.20; 95% confidence interval (95% CI), 3.40-7.96; P for trend <0.001] and also with site-specific sun exposure (OR for top quartile, 5.12; 95% CI, 3.35-7.83; P for trend <0.001). Older age (OR at >70 years, 7.69; 95% CI, 5.14-11.52; P for trend < 0.001) and having more than 10 back nevi (OR, 0.77; 95% CI, 0.61-0.97; P = 0.03) were independently associated with solar elastosis.

Conclusion: Solar elastosis had a strong association with higher site-specific UVE dose, older age, and fewer nevi.

Impact: Solar elastosis could be a useful biomarker of lifetime site-specific UV. Future research is needed to explore whether age represents more than simple accumulation of sun exposure and to determine why people with more nevi may be less prone to solar elastosis.

Figure 1

Cumulative site-specific UVE dose in MJ/m²: Mean, median and interquartile range experienced at the body site by participants in GEM centers (NSW, New South Wales; TAS, Tasmania, Australia; S CAL, Southern California; N CAR, North Carolina; NJ, New Jersey, BR COL, British Columbia, Canada; ONT, Ontario, Canada; TOR, Torino, Italy). Site-specific UVE dose was calculated as total ambient UVE (estimated by NCAR for each participant’s place of residence at each decade of age) for an assumed average 8 hours a day multiplied by the proportion of total sun exposure hours that the site was exposed for each participant. This sun exposure measure takes into account both site-specific sun exposure behavior and ambient UV irradiance.

Figure 2

ORs for solar elastosis on all body sites in 2,304 GEM participants: cumulative sun exposure measures in eight ordered categories containing equal numbers of participants in models adjusted for age, sex, center, pigmentary characteristics and nevi; site-specific exposure also adjusted for body site (head and neck, trunk, arms, legs). Total hours and site-specific hours of sun exposure were reported by participants; site-specific UVE was calculated as total ambient UVE for an assumed average 8 hours a day multiplied by the proportion of total sun exposure hours that the site was exposed for each participant.