Hypothesis: hair cover can protect against invasive melanoma on the head and neck (Australia)

摘要

The anatomic distribution of cutaneous melanoma reflects people’s levels and patterns of sun exposure. While examining trends of incident invasive melanomas by site in recent decades in Australia we noted significant increases in incidence on the ears but not the face or any other site in women younger than 40 years, by 6% (95% confidence interval [CI] 2–10%) per year, and 40–59 years by 7% (95% CI 4–10%) per year. Men of the same age showed no corresponding changes in ear melanoma. However incidence rates of ear melanoma in general were fourfold higher in males than females in Australia. Further, using data from the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program, rates of invasive melanoma on the ear were found to be sevenfold higher in males than females in the US population in the same period. Higher rates of scalp and neck melanomas were also seen in men and women in both populations. We therefore speculated that the isolated rises of ear melanoma in younger women in Australia, and the higher overall rates of ear, scalp and neck melanoma in men compared with women, reflect differences in hair coverage. We tested the specific hypothesis that hair cover reduces sun exposure of the ears using experimental manikins and found that hair cover of the ear reduced solar ultraviolet-B exposure by 81% [SE ±8] compared with uncovered ears. We conclude that hair cover can protect against invasive melanoma on the ear and may similarly protect on the scalp and neck. When discretionary, hair may be an important additional factor to be considered for melanoma prevention.