Posted online December 6, 2010 on www.jco.org
A study of more than 1,600 adults in Australia found that regular use of sunscreen reduced the risk of developing melanoma - the deadliest form of skin cancer - by half, including nearly three-quarters fewer cases of the more dangerous invasive type of melanoma. It is thought to be the first such randomized trial to examine the use of sunscreen in preventing melanoma.
While melanoma accounts for only 5 percent of skin cancer cases, it accounts for the majority of deaths. Sun exposure has long been associated with melanoma, but previous studies of sunscreen use and melanoma risk have been inconclusive, and the use of sunscreen as a preventative has been unclear.
In the study, investigators randomly assigned 1,621 residents aged 25 to 75 in Nambour, Queensland, Australia, to either daily sunscreen use or a person's usual level of sunscreen use on the head and arms for five years. The researchers followed study subjects for a decade after the end of the active trial, through yearly or twice-a-year questionnaires that focused on new skin cancers, sunscreen use and average time spent outdoors, and monitored regional pathology laboratories and a cancer registry for new reported melanomas as well. They gauged both sun exposure and past skin cancers in both groups at the beginning of the trial and in the decade-long follow-up, finding that sun exposure continued to be the same in both groups. They also found that those participants who had been randomized to use sunscreen daily were somewhat more likely to continue to do so after the trial than those in the other group.
In the follow-up, the team identified 22 new melanomas in the usual sunscreen use group and 11 in the daily sunscreen use group. Of these new melanomas, they found 11 invasive melanomas in the usual sunscreen use group compared to only three among the daily sunscreen users, or 73 percent fewer.
Green cautioned that the study included adults only, and suggested a long-term study of the potential benefit of using sunscreen in youth.
What This Means for Patients
In what is thought to be the first randomized clinical trial examining the effect of sunscreen on the development of melanoma, the deadliest form of skin cancer, investigators found half as many melanomas a decade later among regular sunscreen users compared to those who used it less frequently at their own discretion. There were also nearly three-quarters fewer cases of more dangerous invasive melanomas. While previous trials have been unclear about the preventative effects of sunscreen, these results provide evidence for the potential importance of regular use.