Melanoma

The same single RCT also evaluated the effect of sunscreen on the incidence of melanoma, though the trial was not originally designed to test this association. Comments on this analysis also point out that there are other limitations in this trial design, such as where the sunscreen was applied in relation to where melanoma typically arises.6 However, as with nonmelanoma skin cancer, to date, this is the only RCT on sunscreen use. Ten years after the trial ended, daily sunscreen use trended toward being protective against melanoma, but was not significant (HR, 0.50; 95% CI, 0.24-1.02).

A meta-analysis that included 25 studies on melanoma, specifically (including that single RCT by Green and colleagues), found no association between sunscreen use and the risk of melanoma (pooled OR, 1.10; 95% CI, 0.92-1.33).5

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Individually, the results of each of these studies were mixed, with studies conducted in the 1980s and 1990s showing a significant association between sunscreen use the incidence of melanoma. However, studies conducted in the 2000s have shown no association.

Another meta-analysis reported data according to study design and demonstrated that sunscreen was protective against melanoma in hospital-based case-control studies (OR, 0.57; 95% CI, 0.37-0.87) and an ecological study (RR, 0.48; 95% CI, 0.35-0.66), with no association in the RCT (HR, 0.49; 95% CI, 0.24-1.01) and among population-based case-control studies (OR, 1.17; 95% CI, 0.90-1.51).7 Sunscreen use increased the risk of melanoma only in the cohort studies (HR, 1.27; 95% CI, 1.07-1.51).

Conclusions

Although few studies conclusively demonstrate that sunscreen use is protective against developing skin cancers, several meta-analyses of multiple studies suggest that sunscreen use does not cause nonmelanoma skin cancers or melanoma.

However, the mixed results of individual studies highlight the difficulties of evaluating the effect of sunscreen use on cancer incidence because it is difficult to account for recall bias of sunscreen use, misuse of sunscreen, and that individuals more susceptible to skin cancer are more likely to use sunscreen.7,8 In addition, many studies evaluated older sunscreens that were not broad spectrum and therefore did not provide protection against UV-A.

It has been suggested that because they prevented sunburn or prolonged the time to sunburn, people accumulated more UV-A exposure without protection.8 These limitations and the consistently mixed findings from various types of studies make it difficult to draw definitive conclusions about the effect of sunscreen on preventing skin cancers, and indicates that good-quality studies of newer, broad-spectrum sunscreens are needed.

References

  1. Yeager DG, Lim HW. What’s new in photoprotection: a review of new concepts and controversies. Dermatol Clin. 2019;37(2):149-157.
  2. American Academy of Dermatology. Sunscreen FAQs. Accessed April 15, 2019.
  3. Green A, Williams G, Neale R, et al. Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial. Lancet. 1999;354(9180):723-729.
  4. van der Pols JC, Williams GM, Pandeya N, Logan V, Green AC. Prolonged prevention of squamous cell carcinoma of the skin by regular sunscreen use. Cancer Epidemiol Biomarkers Prev. 2006;15(12):2546-2548.
  5. da Silva ES, Tavares R, Paulitsch FDS, Zhang L. Use of sunscreen and risk of melanoma and non-melanoma skin cancer: a systematic review and meta-analysis. Eur J Dermatol. 2018;28(2):186-201.
  6. Green AC, Williams GM, Logan V, Strutton GM. Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol. 2011;29(3):257-263.
  7. Rueegg CS, Stenehjem JS, Egger M, et al. Challenges in assessing the sunscreen-melanoma association. Int J Cancer. 2019;144(11):2651-2668.
  8. Burnett ME, Wang SQ. Current sunscreen controversies: a critical review. Photodermatol Photoimmunol Photomed. 2011;27(2):58-67.