Sunscreen use in adults is beneficial in preventing melanoma
Authors: Mary Kay Barton
Journal: CA A Cancer Journal for Clinicians (2011)

Although the use of sunscreen to prevent squamous cell carcinomas of the skin has been established, the role of sunscreen for the prevention of melanoma has been less clear. Now a new trial suggests that regular sunscreen use helps prevent melanoma (J Clin Oncol. 2011;29:257-263). Adele Green, MD, PhD, and colleagues performed a randomized trial from March 1992 to August 1996 of 1621 randomly selected adult residents of a Queensland township in Australia. The study showed that the rate of developing new melanomas was cut in half by the regular use of sunscreen. Dr. Green, deputy director of the Queensland Institute of Medical Research and professor of epidemiology at the University of Queensland in Brisbane, Australia, says the trial is unique and has clinical implications because there are no other randomized trials studying solely the effect of sunscreen on melanoma prevention in adults. Participants were randomly assigned to either a sunscreen intervention group or a control group using sunscreen at their discretion. The intervention group was given free, broad-spectrum, sun protection factor (SPF) 16 sunscreen and asked to apply it to their head, neck, arms, and hands every morning, with reapplication after long sun exposure, heavy sweating, or bathing. Placebo was not used for the discretionary group because it was considered unethical, especially in view of the subtropical location. All diagnosed melanomas were reviewed by 2 dermatopathologists using available archival slides. The primary endpoint of the study was the prevention of squamous cell and basal cell carcinomas, and in a previous report investigators showed that sunscreen was effective in that regard (Cancer Epidemiol Biomarkers Prev. 2006;15:2546-2548). The current report evaluates the prevention of melanoma as a secondary endpoint using 10-year follow-up data after the intervention portion of the trial ended. After the trial was completed in 1996, 1339 participants (82%) agreed to stay in a follow-up study and completed once- or twice-yearly surveys about new skin cancers, use of sunscreen, and time spent outdoors. Those who withdrew from active follow-up were followed by monitoring their medical records and, as a double check, the Queensland Cancer Registry was searched to find any other melanoma cases. Participants were also randomized for beta-carotene supplementation, with one-half of participants in each group receiving beta-carotene and one-half receiving placebo. Study participants were randomly assigned to either a sunscreen intervention group or a control group using sunscreen at their discretion. Credit: istock.com. Risk factors for melanoma were well balanced between the study groups, as well as sun exposure and use of other sun protections, such as wearing a hat. Compliance with sunscreen use, assessed by weights of returned bottles and participant reports, was approximately 75%. Approximately 38% of the control group did not use sunscreen and 35% used it only once or twice a week. By the end of 2006, 846 participants (52%) were still completing surveys, 600 (37%) were passive participants, and 173 (11%) had died. Approximately one-quarter of patients who were in the sunscreen intervention group continued regular use of sunscreen, and 18% in the nonintervention group applied it regularly after the trial. From 1993 to 1996, 2 participants in the intervention group and 7 in the control group developed melanoma. In addition, from the trial end in 1996 to 2006, 9 participants in the intervention group and 15 in the control group developed melanoma. In total, 11 participants in the intervention group and 22 in the control group were newly diagnosed with either invasive or in situ melanoma (P = .051). Invasive melanoma incidence was decreased by 73% in the intervention group compared with the control group (3 vs 11 patients, respectively; P = .045). The authors noted, however, that the analysis of only invasive melanoma was exploratory and therefore should be interpreted cautiously. The overall estimate for the effectiveness of sunscreen did not appreciably change when a multivariate proportional hazards analysis was performed, taking into consideration sex, age, skin type, numbers of nevi, history of skin cancer, and sun exposure. The low use of sunscreen in the control group was striking, especially given the sunny climate of Queensland. Dr. Green points out that there have been studies showing that younger people use more sun protection than older generations. She says clinicians and public health organizations should consider increasing awareness of the long-term damage that intense sun exposure may cause, including premature skin aging, benign skin tumors, and cancers, as well as the many harms to the eyes. “[Creating awareness] is an important step so that people can become personally motivated to practice sun protection and thus lower their chances of developing these problems,” she says. The study showed a decrease in melanomas on all body sites, not just the areas of prescribed application of sunscreen. According to the authors, this is likely due to the more generalized application of sunscreen to the trunk and limbs in the intervention group. Beta-carotene supplementation did not appear to have any bearing on the development of melanoma, with 16 cases occurring in those receiving supplements and 17 in those receiving placebo. “One of the very important clinical implications of the study findings is that relatively recent sun exposure in adulthood is an important causal factor for melanoma, and this seems to be as true for melanomas on the trunk and limbs as well as on the head and neck,” Dr. Green says. “The corollary follows that primary melanoma prevention is possible in adulthood—that is, it is never too late to start routine sun protection measures.” In an accompanying editorial, Phyllis Gimotty, PhD, and Karen Glanz, PhD, MPH, professors in biostatistics and epidemiology, respectively, at the University of Pennsylvania School of Medicine in Philadelphia, point out that although practitioners often routinely recommend sunscreen use, instructions for optimal use are not usually given. In the editorial, Drs. Gimotty and Glanz emphasize the clinical implications. Patients at high risk for melanoma based on skin characteristics or family history, or who live in sunny climates, for example, should be advised to routinely put on sunscreen as a habit, they state. In addition, clear instructions need to be given for the use of sunscreen similar to that done in the current study, and parents should apply sunscreen to their children as well as to themselves, they write. “The question of its efficacy with respect to melanoma prevention should no longer deter scientists or clinicians from recommending sunscreen use,” they state. Dr. Glanz says she and her colleagues are currently working on updating a previously published synthesis of the evidence base for the Guide to Community Preventive Services (Am J Prev Med. 2004;27:422-466) to include the results of new studies. She says attitudes toward sunscreen use and other sun protection practices can change, although it is likely to be gradual. Dr. Green concurs that no substantial shift in cultural norms will occur without a long lead time, and adds that the full and ongoing commitment of health workers and policy makers is a necessity.