Am Fam Physician. 2010;82(8):989-990
Author disclosure: Nothing to disclose.
Clinical Question
Does sunscreen use prevent skin cancer?
Evidence-Based Answer
Daily sunscreen use reduces the incidence of squamous cell carcinoma but not the incidence of basal cell carcinoma. (Strength of Recommendation [SOR]: B, based on a single randomized controlled trial with less than 13 years of follow-up). It is unclear whether there are longer-term effects. There is no consistent, conclusive evidence that sunscreen use prevents melanoma. (SOR: C, meta-analysis of case-control studies).
Evidence Summary
SQUAMOUS CELL CARCINOMA
In a randomized controlled trial, 1,621 participants in Nambour, Australia, were randomized to one of four treatment groups. Of the two groups assigned to daily sunscreen use, one group (n = 404) applied sun protection factor (SPF) 15 sunscreen to the head, neck, arms, and hands, and received daily oral beta carotene supplementation. The second group (n = 408) was assigned to sunscreen application plus an oral placebo. Of the two groups not assigned to daily sunscreen use, one group (n = 416) received daily oral beta carotene supplementation, and the other group (n = 393) received daily oral placebo. Participants who were not in the daily sunscreen groups were allowed discretionary use of sunscreen.1
Over 4.5 years, persons in the daily sunscreen groups had a decreased incidence of squamous cell tumors at the sites of sunscreen application compared with those in the no daily sunscreen groups (28 tumors in 22 persons versus 46 tumors in 25 persons; rate ratio [RR] = 0.61; 95% confidence interval [CI], 0.46 to 0.81; number needed to treat = 140).1 Each group included persons of all skin types, with more than 50 percent of persons in each group having fair skin and 20 percent reporting that they “always burn.” An intention-to-treat analysis of 1,383 participants eight years after completion of the initial randomized controlled trial demonstrated a prolonged protective effect, with a 35 percent lower incidence of squamous cell carcinoma in the daily sunscreen groups (RR = 0.65; 95% CI, 0.43 to 0.98; number needed to treat = 2.8).2
BASAL CELL CARCINOMA
In the Nambour study, the incidence of basal cell carcinoma in the daily sunscreen groups compared with the no daily sunscreen groups was not statistically significant after 4.5 years (153 tumors in 65 persons versus 146 tumors in 63 persons; RR = 1.05; 95% CI, 0.82 to 1.34).1 In the eight-year follow-up study, there was no statistically significant decrease in the incidence of basal cell carcinoma (RR = 0.75; 95% CI, 0.49 to 1.14).2 In an additional multifailure survival analysis, none of the three analysis models found a significant difference in the risk of subsequent basal cell carcinoma.3
MELANOMA
A meta-analysis of 11 case-control studies involving 9,067 patients evaluated the effect of sunscreen use on the incidence of melanoma.4 Results were heterogeneous and included study data from population-based and hospital-based sources. The analysis did not find an altered rate of melanoma with sunscreen use (combined RR = 1.11; 95% CI, 0.37 to 3.32). A review of 18 case-control studies examining sunscreen use in patients with melanoma found no significant association between melanoma and sunscreen use after controlling for skin sensitivity.5
Recommendations from Others
The American Academy of Dermatology recommends year-round application of broadspectrum sunscreen with SPF 30 or higher to all areas of the body exposed to the sun.6
