Sunscreen and Skin Cancer Prevention: What the Evidence Shows

The Key RCT - Nambour Skin Cancer Study (Australia)

• Melanoma: Daily sunscreen group had 11 new melanomas vs. 22 in the discretionary group - a 50% reduction (HR 0.50, 95% CI 0.24-1.02, p=0.051). Just missed statistical significance overall, but...
• Invasive melanoma was significantly reduced: only 3 vs. 11 cases (HR 0.27, 95% CI 0.08-0.97) - a 73% reduction in invasive disease.
• Prior publications from the same trial had already confirmed a ~40% reduction in squamous cell carcinoma (SCC) with daily SPF 15+ sunscreen.

Meta-Analyses and Systematic Reviews

1. Silva et al. (2018) - European Journal of Dermatology | PMID 29620003

• 29 studies, 313,717 participants, 10,670 cases
• Overall result: No significant association (OR 1.08; 95% CI 0.91-1.28)
• Both melanoma and NMSC were non-significant pooled
• Importantly: early pre-1980s studies showed a positive association (OR 2.35) - people using sunscreen had MORE melanoma, but this reversed and studies from the 1990s onward showed the association narrowed to null
• Conclusion: Does not confirm protective benefit, but also no increased risk. Observational data is heavily confounded (people use sunscreen because they have high sun exposure).

2. Rueegg et al. (2019) - International Journal of Cancer | PMID 30447006

• 28 studies, 21,069 melanoma cases
• Found marked heterogeneity by study design:
  • Hospital-based case-control studies: OR 0.57 (CI 0.37-0.87) - significant protective effect
  • Population-based case-control studies: OR 1.17 (no effect)
  • Cohort studies: HR 1.27 (slight positive association - confounding by indication)
  • The single RCT: HR 0.49 (CI 0.24-1.01) - near-significant protection
• Adjusting for sun exposure, sunburns, and phenotype consistently moved estimates toward protection
• Key insight: Confounding by indication (sun-exposed people use sunscreen more) inflates observational risk. When properly adjusted, evidence tilts protective.

3. Brunner et al. (2025) - Anticancer Research | PMID 40876975 - Most Recent

• 23 studies, ever vs. never sunscreen use for melanoma
• OR 0.98 (95% CI 0.79-1.21, p=0.83) - no significant association
• Significant heterogeneity unexplained by subgroup analyses
• Asymmetric funnel plot suggests publication bias
• Conclusion: Cannot confirm protective effect; methodological issues in existing studies limit conclusions

4. Rönsch & Bauer (2021) - Systematic Review of RCTs only | PMID 34698024

• Restricted to controlled and randomized trials (higher quality)
• Actinic keratoses: All 4 studies showed significant benefit
• SCC: Both studies showed significant benefit
• BCC: No significant effect (though non-significant trend toward protection)
• Photoageing: Significant benefit in both studies

Summary Table

Why Observational Meta-Analyses Show Null Results

Bottom Line

• SCC and actinic keratoses: Clear, RCT-supported benefit from regular sunscreen use.
• Melanoma: The best single study (Nambour RCT) shows a ~50% reduction; meta-analyses of observational studies show null results due to confounding, not because sunscreen doesn't work.
• BCC: No proven benefit yet.
• The Skin Cancer Foundation summarizes the evidence as: SPF 15+ daily use reduces SCC risk by ~40% and melanoma risk by ~50%, based on the Nambour trial data.