Challenges in assessing the sunscreen-melanoma association

Area of Science:

• Dermatology
• Epidemiology
• Oncology

Background:

• The relationship between sunscreen use and melanoma risk is debated, with conflicting findings in existing research.
• Systematic reviews are crucial for synthesizing evidence and addressing heterogeneity in observational studies.

Purpose of the Study:

• To systematically review and meta-analyze studies investigating the association between sunscreen use and melanoma risk.
• To identify and account for sources of heterogeneity and bias in the evidence.

Main Methods:

• Systematic search for original articles on sunscreen-melanoma association in humans up to February 2018.
• Random-effects meta-analysis stratified by study design (case-control, ecological, cohort, RCT).
• Meta-regression to explore sources of heterogeneity and interaction effects.

Main Results:

• Included 28 studies with 21,069 melanoma cases; significant heterogeneity observed across study designs.
• Inverse association between sunscreen use and melanoma found in hospital-based case-control studies, ecological study, and RCT.
• No association in population-based case-control studies; positive association in cohort studies.
• Association varied by latitude, region, adjustment for naevi/freckling, and proportion of non-users.

Conclusions:

• Evidence from observational studies on sunscreen use and melanoma risk is weak and heterogeneous.
• Challenges in controlling for confounding by indication complicate interpretation of observational data.
• The single randomized controlled trial indicated a protective effect of sunscreen against melanoma.