High sun protection factor sunscreens in the suppression of actinic neoplasia

A controlled trial was undertaken from December 1987 to December 1990 to test the hypothesis that a strong sunscreen can reduce the number of cancerous and precancerous skin lesions. Candidates were selected from a high-risk population attending either a university- or Veterans Affairs-based dermatology practice in Lubbock, Tex, for a prospective, double-blind, controlled trial of daily application of sunscreen vs placebo over a 2-year period. Participants were asked to volunteer if they had demonstrated premalignant changes (actinic keratoses) or nonmelanoma skin cancer (basal cell carcinoma or squamous cell carcinoma), had continuing sun exposure, and were not using sunscreen on a regular basis. Fifty-three volunteers were initially enrolled in the study, and 37 came for the final 24-month visit.

The rate of appearance of new precancerous skin lesions was less for the treatment group than for control subjects. People with darker skin had fewer actinic keratoses, women had fewer lesions than men, and people with fewer lesions at enrollment had fewer lesions during the study. The numbers of new nonmelanoma skin cancers appearing during the study period were too small for statistical analysis.

The regular use of sunscreens can significantly reduce cutaneous neoplasia, as indicated by its suppression of precancerous lesions. A longer and/or larger study would be necessary to demonstrate an effect on malignant lesions.