Prevention of Melanoma With Regular Sunscreen Use

Abstract

EVIDENCE FROM RANDOMIZED CONTROLLED TRIALS demonstrated that regular sunscreen use prevents cutaneous squamous cell carcinoma. Until now, there were no randomized controlled trial data on the effects of sunscreen use in melanoma prevention, and case-control studies yielded conflicting results. The community-based skin cancer prevention trial conducted by Green et al in the subtropical region of Nambour, Queensland, Australia, provided evidence from a randomized controlled trial that regular use of sunscreen prevents melanoma. The study included 1621 adults randomized to regular sunscreen use or to discretionary use, which included no use at all. Those randomized to regular sunscreen use were given an unlimited supply of broad-spectrum sunscreen with a sun protection factor (SPF) of 16 and asked to apply it to the head, neck, arms, and hands every morning. Reapplication was advised after heavy sweating, bathing, or long sun exposure. The regular application of a broad-spectrum sunscreen with an SPF of 16 during a 5-year treatment period reduced the incidence of new primary melanomas during a subsequent 10-year follow-up period. In the 10 years after trial cessation, 11 new primary melanomas were identified among the 812 persons assigned to the daily sunscreen group, compared with 22 melanomas among the 809 persons assigned to the discretionary group. According to the authors, this “represented a reduction of the observed rate in those randomly assigned to daily sunscreen use (hazard ratio [HR], 0.50; 95% confidence interval [CI], 0.24-1.02; P = .051).” The reduction in invasive melanomas was substantial (3 in the daily-use group vs 11 in the discretionary-use group; HR, 0.27; 95% CI, 0.08-0.97; P=.045). Dailyand discretionary-use groups were similar for known risk factors, including skin color, outdoor behavior, sunburn history, nevus density, and history of skin cancer at the start of the trial. Sun exposure and use of other forms of sun protection, such as hat wearing and shade seeking, were similar between the groups during the trial. Adherence with sunscreen use as assessed by the selfreported frequencies of application, participant diaries, and weight of returned sunscreen bottles was high among the regular sunscreen users. Approximately 75% of the regular users applied sunscreen daily; 25% of this group also applied sunscreen to nonintervention sites (trunk, lower limbs, or both). The reduction in melanomas in all body sites may reflect the tendency of participants in the daily sunscreen group to apply sunscreen to the torso and lower limbs without being asked. Since exposure to UV radiation (UVR) is the only known modifiable cause of melanoma, this study is a potential “game changer” for the primary prevention of melanoma. Patients at high risk for skin cancer because of phenotypic characteristics (fair skin, freckling, and tendency to sunburn) who live in or visit sunny climates or who have a family history of melanoma should routinely and thoroughly apply sunscreen before going outside. In the United States, this recommendation is particularly relevant to those who reside in locations with relatively high levels of ambient UVR, such as Arizona, California, and Florida, and those living in temperate climates, who often vacation in sunny places during the winter and experience seasonal variations in ambient UVR. The US Preventive Services Task Force concluded that randomized controlled trials suggest counseling can increase sun-protective behaviors and decrease indoor tanning. Counseling should consist of inquiring about at-risk individuals’ current habits of sun exposure and willingness to consider using sunscreen regularly. Instructing individuals on the proper use of sunscreens is important. Two coats or about 1 full teaspoon of sunscreen should be applied to each body part prior to going outside: head, neck, and ears; front of trunk; back of trunk; each arm, dorsum of hand, and shoulder; and each lower leg, upper leg, and dorsum of foot. The leg needs to be divided into upper and lower segments with each getting 1 teaspoon. If the person is sweating heavily or towels off after exercise or swimming, it is necessary to