Reduction of Solar Keratoses by Regular Sunscreen Use

The incidence of and mortality from skin cancer are increasing in many countries. In view of the added concern about ozone depletion, many organizations are promoting the regular use of sunscreens to prevent skin cancer, despite the absence of evidence that these products have this effect. Solar (actinic) keratosis is a precursor of squamous-cell carcinoma of the skin. We conducted a randomized, controlled trial of the effect on solar keratoses of daily use of a broad-spectrum sunscreen cream with a sun-protection factor of 17 in 588 people 40 years of age or older in Australia during one summer (September 1991 to March 1992). The subjects applied either a sunscreen cream or the base cream minus the active ingredients of the sunscreen to the head, neck, forearms, and hands. The mean number of solar keratoses increased by 1.0 per subject in the base-cream group and decreased by 0.6 in the sunscreen group (difference, 1.53; 95 percent confidence interval, 0.81 to 2.25). The sunscreen group had fewer new lesions (rate ratio, 0.62; 95 percent confidence interval, 0.54 to 0.71) and more remissions (odds ratio, 1.53; 95 percent confidence interval, 1.29 to 1.80) than the base-cream group. There was a dose-response relation: the amount of sunscreen cream used was related to both the development of new lesions and the remission of existing ones. Regular use of sunscreens prevents the development of solar keratoses and, by implication, possibly reduces the risk of skin cancer in the long term., The incidence of skin cancers (melanoma and nonmelanoma) has been increasing in many countries recently,¹–³ and may be increased more in the future by ozone depletion⁴. Many public health authorities are initiating primary prevention programs recommending the regular use of sunscreens that absorb ultraviolet radiation. Sunscreens reduce the frequency of tumors induced experimentally in animals exposed to ultraviolet radiation⁵,⁶. Despite the fact that sunscreens are commercially available and widely advocated for the prevention of skin cancer in humans, it is not known whether their use has any effect on the incidence of either nonmelanoma or melanoma…