Challenges in assessing the sunscreen‐melanoma association

Abstract

Whether sunscreen use affects melanoma risk has been widely studied with contradictory results. To answer this question we performed a systematic review of all published studies, accounting for sources of heterogeneity and bias. We searched for original articles investigating the sunscreen‐melanoma association in humans to February 28, 2018. We then used random‐effects meta‐analysis to combine estimates of the association, stratified by study design. Stratified meta‐analysis and meta‐regression were used to identify sources of heterogeneity. We included 21,069 melanoma cases from 28 studies published 1979–2018: 23 case–control (11 hospital‐based, 12 population‐based), 1 ecological, 3 cohort and 1 randomised controlled trial (RCT). There was marked heterogeneity across study designs and among case–control studies but adjustment for confounding by sun exposure, sunburns and phenotype systematically moved estimates toward decreased melanoma risk among sunscreen users. Ever‐ vs . never‐use of sunscreen was inversely associated with melanoma in hospital‐based case–control studies (adjusted odds ratio (OR) = 0.57, 95%confidence interval (CI) 0.37–0.87, p heterogeneity < 0.001), the ecological study (rate ratio = 0.48, 95%CI 0.35–0.66), and the RCT (hazard ratio (HR) = 0.49, 95%CI 0.24–1.01). It was not associated in population‐based case–control studies (OR = 1.17, 95%CI 0.90–1.51, p heterogeneity < 0.001) and was positively associated in the cohort studies (HR = 1.27, 95%CI 1.07–1.51, p heterogeneity = 0.236). The association differed by latitude ( p interaction = 0.042), region ( p interaction = 0.008), adjustment for naevi/freckling ( p interaction = 0.035), and proportion of never‐sunscreen‐users ( p interaction = 0·012). Evidence from observational studies on sunscreen use and melanoma risk was weak and heterogeneous, consistent with the challenges of controlling for innate confounding by indication. The only RCT showed a protective effect of sunscreen.

The efficacy and safety of sunscreen use for the prevention of skin cancer

“…20 Recent meta-analyses have not supported the findings of these RCTs, finding no significant effectiveness of sunscreen for preventing either melanoma or nonmelanoma skin cancers. 21,22 However, these meta-analyses included studies with retrospective designs with methodological inconsistencies among studies, and 1 included studies that used only UVB filters (rather than broad-spectrum sunscreens). 21 Overall, the highest-quality evidence available suggests that sunscreens do prevent skin cancer.…”

Art of prevention: The importance of melanoma surveillance

“…Randomized controlled trials on the safety and efficacy of sunscreen for the prevention of cutaneous cancers are difficult because people who are more likely to use sunscreens are also more likely to have sun exposure. Prior meta-analyses have found null or even a positive association of sunscreen use and cutaneous melanoma risk ( Rueegg et al, 2019 ). An increasing body of evidence supports the use of sunscreen as a form of secondary prevention.…”

Solkrem og maligne melanomer

“…Vi vet rett og slett ikke om solkrem kan øke eller redusere insidens og dødelighet av maligne melanomer I noen tidligere analyser har man funnet en positiv assosiasjon mellom malignt melanom og bruk av solbeskyttende hudkremer, altså at bruk av solkremer øker risikoen for maligne melanomer, men nyere metaanalyser finner ingen slik sammenheng (20,21). Vi vet rett og slett ikke om solkrem kan øke eller redusere insidens og dødelighet av maligne melanomer.…”