For the First Time, Sunscreen Shown to Reduce Melanoma

RCT with nearly 15-year data

Nick Mulcahy

January 25, 2011

January 25, 2011 — Melanoma in adults might be preventable with the regular use of sunscreen — that is, with the daily application to the head, neck, arms, and hands, according to Australian researchers who conducted a rare randomized controlled trial of sunscreen use.

The study randomized 1621 adults to regular sunscreen use or to discretionary use, which included no use at all.

The regular application of sunscreen with a sun protection factor of 15 or more during a 5-year treatment period reduced the incidence of new primary melanomas during a subsequent 10-year follow-up period, report the study authors, led by Adele Green, MB BS, PhD, from the University of Queensland in Brisbane.

"Our findings provide reassurance . . . about sunscreen's ability to prevent melanoma," write Dr. Green and her colleagues in the January 20 issue of the Journal of Clinical Oncology.

Two editorialists, who wrote an essay that accompanies the study, mostly endorse the findings.

"The question of its efficacy with respect to melanoma prevention should no longer deter scientists or clinicians from recommending sunscreen use," write Phyllis Gimotty, PhD, and Karen Glanz, PhD, MPH, from the University of Pennsylvania School of Medicine in Philadelphia.

However, Dr. Gimotty and Dr. Glanz, who are cancer epidemiologists, quibble about the study statistics, saying that the study's P values "could be considered of borderline significance."

But these experts in statistical methods ultimately yield to the study authors' conclusions. "The trial's findings are the first to provide strong evidence for a reduction in the incidence of invasive melanoma after regular application of broad-spectrum sunscreen in adults," the pair write.

Highest Rate of Skin Cancer in the World

The new findings come from the Nambour Skin Cancer Prevention Trial, which was conducted in Queensland — a region with "the highest rate of skin cancer in the world," the editorialists point out.

Dr. Green and her colleagues previously reported that regular sunscreen use during the initial 5-year study period prevented squamous cell carcinomas of the skin (Cancer Epidemiol Biomarkers Prev. 2006;15:2546-2548).

In their current paper, the authors report results at 10 years after that 5-year trial ended. In the 10 years after trial cessation, 11 new primary melanomas were identified in the daily sunscreen group, compared with 22 in the discretionary group. This represents 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 to 1.02; = .051).

Furthermore, an exploratory analysis indicated that there was a "substantial" reduction in invasive melanomas (3 cases in the regular use group and 11 in the control group; HR, 0.27; 95% CI, 0.08 to 0.97; P =.045), compared with that for preinvasive in situ melanomas (8 vs 11 cases; HR, 0.73; 95% CI, 0.29 to 1.81; P = .49).

The study findings are not limited to Australians, say the authors.

"They also have implications for white people living in temperate climates in North America and Europe," they write, adding that such people might have an increased risk for melanoma because of "their predilection for holidays in sunny places."

How to Apply and Reapply Daily Sunscreen

The editorialists make a set of recommendations to clinicians on the basis of the trial's landmark findings. But before doing so, they say that this study is something special.

"The trial was an ambitious and unique study," they write. "It is unlikely that another trial of comparable scope and rigor will be conducted in the foreseeable future."

One of the study's lessons is that "clear instructions" to the public are needed about "use and reapplication." In the study, the 812 men and women randomized to sunscreen intervention were given a free unlimited supply of broad-spectrum sunscreen (8% [by weight] 2-ethylhexyl p-methoxycinnamate and 2% [by weight] 4-tert-butyl-4′-methoxy-4-dibenzoylmethane) with a sun protection factor of 16.

"They were asked to apply it to head, neck, arms, and hands every morning (and reapplication was advised after heavy sweating, bathing, or long sun exposure)," write the authors.

This part of the study is important because, as the editorialists point out, surveys indicate that pediatricians regularly advise parents to have children wear sunscreen when playing outdoors, but "usually do not give advice about optimal use and reapplication."

The editorialists also advise, as many experts do, "patients at high risk for skin cancer because of phenotypic characteristics (fair skin, freckling, tendency to sunburn, and so on), who live in or visit sunny climates, and/or who have a family history of melanoma to routinely and thoroughly apply sunscreen before going outside."

The regular use of sunscreen should become a "habit" for high-risk and highly exposed adults and children, say Dr. Gimotty and Dr. Glanz.

However, they also point out that "sunscreen use alone will not likely reduce the incidence of skin cancer."

These latest findings should not be an excuse to drop other sun protections, the editorialists write. "Excess exposure to ultraviolet rays should be avoided, clothing should be used to shield skin from the sun, and sun-safe environments should be used for outdoor recreation," they write.

Latent Effect

Compliance was fairly high in the study among the regular sunscreen users, say the authors. Compliance was assessed using the average self-reported frequencies of application, participant diaries, and the weight of returned sunscreen bottles.

Approximately 75% of the regular users complied and used sunscreen daily; 25% of this group also applied sunscreen to nonintervention sites (trunk and/or lower limbs).

Because it would have been unethical to have had a placebo sunscreen as part of the study, the investigators had the control group consist of men and women who used sunscreen at their own discretion. The majority of participants in the control group either did not apply sunscreen (38%) or applied it once or twice a week at most (35%); 8% applied it to nonintervention sites, report the authors.

Sun exposure was similar between the regular- and discretionary-use groups during the trial, the authors report. Use of sun protection measures other than sunscreen was also similar during the trial — approximately 60% of both groups usually sought shade and around 75% usually wore a hat.

The prevention of melanoma indicated by the study might point to a latent of effect of sunscreen, suggest the authors, because most of the regular sunscreen users stopped the daily application of sunscreen at 5 years.

"On the basis of reports of active participants, 25% of those randomly assigned to daily sunscreen continued to use sunscreen on a regular basis after the trial, compared with 18% of the nonintervention group," write the authors.

Dr. Green reports receiving research funding from L'Oréal Recherche.

J Clin Oncol. 2011.29;249-250, 257-263. Abstract, Abstract

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