We all know that sunscreen is essential for delaying skin aging, preventing sunburn, and reducing the risk of most skin cancers. However, the research is less conclusive as to whether sunscreen can prevent one particular type of skin cancer – melanoma.
Does sunscreen reduce the risk of melanoma? And, if so, why is the research for this weaker than with other skin cancers?
What is Melanoma?
Melanoma is a type of skin cancer that develops from melanocytes (the cells that give your skin its natural colour). It is the least common form of skin cancer but, as it is able to spread to other parts of the body, it is the deadliest.
Risk factors for melanoma include:
- A family history of melanoma
- Fair skin (skin that burns easily when exposed to the sun)
- Having more than 50 moles on your body or having unusual moles
- Excessive UV exposure – particularly the use of tanning beds
- A history of sunburn – particularly in childhood
So, if UV exposure and sunburn are risks for melanoma, then surely sunscreen use should reduce these risks?
Right?
The Relationship Between Sunscreen & Melanoma
Despite increasing knowledge of the importance of sunscreen for preventing skin cancers, the rates of melanoma continue to rise [1].
As UV exposure and sunburn are risk factors for melanoma, it would be reasonable to assume that the use of sunscreen to reduce sun exposure would lead to reduced rates of melanoma.
However, the majority of research has found the opposite to be true, with many studies concluding that sunscreen use is associated with increased melanoma risk [2].
Other research suggests that sunscreen users, compared to those who do not use sunscreen, may be more likely to develop sunburn [3].
UVA vs UVB
UV radiation can be broken down into UVA, UVB, and UVC, with the latter unable to penetrate the atmosphere and thus not posing a risk to health.
UVB rays have more energy than UVA rays but can only penetrate the epidermis where they cause sunburn and directly damage DNA.
Due to this, UVB radiation has long been associated with skin cancer and the longer, less energetic UVA rays (which take a lot longer to burn skin) have been largely ignored. However, more recently, it has become apparent that UVA radiation can indirectly damage DNA through the generation of free radicals.
UVA radiation accounts for the majority of UV radiation and is present all year round at consistent levels – compared to UVB radiation which is stronger in the summer months (hot and sunny weather) and at its peak in the middle of the day.
Why Is This Distinction Important?
A lot of the research that concluded that sunscreen use increased the risk of melanoma used sunscreens that had little to no UVA protection. Combined with the fact that many studies have highlighted that sunscreen is often used to extend periods of time in the sun – the individuals in these studies are likely exposing themselves to more UVA radiation.
Improper Use Of Sunscreen
One reason for the inconsistent relationship between sunscreen use and melanoma risk is down to how people use sunscreen. As mentioned above, multiple studies have identified that sunscreen is often used to extend periods of time in the sun and, thus, increase UV exposure.
Two European studies found that sunbathers who used a sunscreen with SPF30 spent 19-25% longer sunbathing than those who used an SPF10 [4]. In addition, sunscreen users are more likely to develop sunburn than their non-sunscreen using counterparts. In fact, in one study, 66% of those who had sunburn had used sunscreen to prolong their time in the sun [5].
Does Sunscreen Reduce The Risk Of Melanoma?
The findings that sunscreen use increases the risk of melanoma can generally be explained by the following:
- Sunscreen is more likely to be used by people who are prone to sunburn (and, thus, at a higher risk of melanoma in the first place)
- Sunscreen is often used to extend periods of time in the sun/sunbathing without burning
- At the time a lot of studies were conducted, the dangers of UVA radiation were less known and sunscreens generally contained little to no UVA protection.
However, when sunscreen is used correctly, it can reduce the incidence of melanoma by 50-73% [6]. This research compared regular, daily use of a broad-spectrum sunscreen to intermittent use of sunscreen (i.e. applied when needed) and suggests that melanoma may be linked to cumulative sun exposure, as well as incidences of sunburn.
Overall, sunscreen use, alone, is not enough to protect against melanoma, but daily use of a broad-spectrum sunscreen in combination with sun-safe behaviours (e.g. using protective clothing, avoiding prolonged sun exposure, avoiding midday sun exposure, seeking shade, etc) may be.
References
- Jemal, A., Siegel, R., Ward, E., Hao, Y., Xu, J. & Thun, M. (2009). ‘Cancer statistics, 2009’, CA Cancer J Clin, 59 (4), 225-249. Available at: https://www.ncbi.nlm.nih.gov/pubmed/19474385/
- Xie, F., Xie, T., Song, Q., Xia, S. & Li, H. (2015). ‘Analysis of association between sunscreens use and risk of malignant melanoma’, Int J Clin Exp Med., 8(2), 2378-2384. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4402823/
- Planta, M. (2011). ‘Sunscreen and Melanoma: Is Our Prevention Message Correct?’, J Am B Fam Med., 24(6), 735-739. Available at: https://www.jabfm.org/content/24/6/735.long
- Autier, P., Boniol, M. & Dore, J. (2007). ‘Sunscreen use and increased duration of intentional sun exposure: still a burning issue’, Int J Cancer., 121(1), 1-5. Available at: https://www.ncbi.nlm.nih.gov/pubmed/17415716?dopt=Abstract
- Koster, B., Thorgaard, C., Phillip, A. et al. (2010). ‘Prevalence of sunburn and sun-related behaviour in the Danish population: A cross-sectional study’, Scandinavian J Pub Health., 38(5), 548-552. Available at: https://journals.sagepub.com/doi/abs/10.1177/1403494810371250
- Green, A., Williams, G., Logan, V. & Strutton, G. (2011). ‘Reduced melanoma after regular sunscreen use: randomized trial follow-up’. Journal of Clinical Oncology, 29(3), 257-263. Available at: https://pdfs.semanticscholar.org/f3ad/3ff1e273eaa425f7b7e1bdb33e67df5dedec.pdf
