Abstract
Regular sunscreen use prevents cutaneous squamous cell carcinoma long term, but the effect on melanoma is highly controversial. We evaluated whether long-term application of sunscreen decreases risk of cutaneous melanoma. In 1992, 1,621 randomly selected residents of Nambour, a township in Queensland, Australia, age 25 to 75 years, were randomly assigned to daily or discretionary sunscreen application to head and arms in combination with 30 mg beta carotene or placebo supplements until 1996. Participants were observed until 2006 with questionnaires and/or through pathology laboratories and the cancer registry to ascertain primary melanoma occurrence. Ten years after trial cessation, 11 new primary melanomas had been identified in the daily sunscreen group, and 22 had been identified in the discretionary group, which represented a reduction of the observed rate in those randomly assigned to daily sunscreen use (hazard ratio [HR], 0.50; 95% CI, 0.24 to 1.02; P = .051). The reduction in invasive melanomas was substantial (n = 3 in active v 11 in control group; HR, 0.27; 95% CI, 0.08 to 0.97) compared with that for preinvasive melanomas (HR, 0.73; 95% CI, 0.29 to 1.81). Melanoma may be preventable by regular sunscreen use in adults.
Highlights
The need for more effective prevention of melanoma is recognized around the world as climbing incidence and high mortality in white populations persist.[1,2,3] In the United States, approximately 68,700 new melanoma occurrences and more than 8,600 deaths were expected to occur in 2009.4 Exposure to solar ultraviolet (UV) radiation is the only established modifiable cause of melanoma.[5,6]Despite the known etiologic role of sun exposure, the question regarding sunscreen use to prevent melanoma remains open[7] and controversial.[8]
Ten years after trial cessation, 11 new primary melanomas had been identified in the daily sunscreen group, and 22 had been identified in the discretionary group, which represented a reduction of the observed rate in those randomly assigned to daily sunscreen use
Nonrandomized studies of the melanoma-sunscreen association are unable to distinguish the main determinants of sunscreen use from those of melanoma, because they are the same—namely, susceptibility to sunburn, high occupational or recreational sun exposure, and family history.[11]
Summary
The need for more effective prevention of melanoma is recognized around the world as climbing incidence and high mortality in white populations persist.[1,2,3] In the United States, approximately 68,700 new melanoma occurrences and more than 8,600 deaths were expected to occur in 2009.4 Exposure to solar ultraviolet (UV) radiation is the only established modifiable cause of melanoma.[5,6]Despite the known etiologic role of sun exposure, the question regarding sunscreen use to prevent melanoma remains open[7] and controversial.[8]. The only relevant evidence comes from a randomized trial of sunscreen application in Canadian children conducted from 1993 to 1996 that showed a small reduction in new melanocytic nevi,[12] the strongest predictors of melanoma, in children allocated to a sunscreen arm, especially if the children had freckles
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