If you were to undertake a critical review of all the available research you would come to the conclusion that sunscreen, as part of a SunSmart regime, does reduce the risk of Melanoma and other skin cancers*.
(*Kernagahn is responding to author Ian Wishart concerns about the lack of evidence that sunscreen prevents melanoma.)
The most robust and current research conducted in Australia and published in the Journal of Clinical Oncology in 2011 does just that and a Norwegian study published in 2016 (see details of both studies below).
The Cancer Society would point out that observational epidemiological studies can be confounded because the people who use the most sunscreen have the fairest skin types (and hence at highest phenotypic risk of melanoma) also spend most time outdoors (and hence at highest environmental risk of melanoma). The society also points out that the only research design that can control such confounding is a randomised controlled trial – which the Australian study was – and that study found that people randomised to use sunscreen on a daily basis had half the melanoma incidence of those who were randomised to applying sunscreen at their own discretion.
But, sunscreen alone is not the solution to preventing skin cancer, the more you minimise the UVA/UBA (sun exposure) the more you minimise the risk of skin cancer, which is why when the UV is high you need to also wear a shirt, hat, sun glasses, and going under shade as they all contribute to reducing your skin cancer risk.
Skin cancer is largely preventable. Over 90% of all skin cancer cases are attributed to excess sun exposure. We encourage all New Zealanders to be SunSmart and to Slip, Slop, Slap and Wrap (not just Slop).
Sunscreen alone is not the solution to preventing skin cancer, as the more you minimise the UV (sun exposure) the more you minimise the risk of skin cancer, so wearing a shirt, hat, sun glasses, and going under shade all contribute to reducing your risk. When you follow the instructions on the sunscreen label, SPF30 filters 96.7% of UV radiation. SPF50+ filters 98% of UV radiation.
How to be SunSmart:
- Slip on a long-sleeved, collared shirt and seek shade, like under a tree.
- Slop on sunscreen that is at least SPF30+, UVA/UVB broad-spectrum and water resistant
- Slap on a broad-brimmed hat that shades your face, head, neck and ears
- Wrap on close fitting sunglasses
- Don’t use sunbeds
When to be SunSmart:
- When the ultraviolet index (UVI) is 3 or above
- From September to April, especially between 10am and 4 pm
- At the beach, as reflections from water and sand can increase UV
- At high altitudes, especially near snow, which strongly reflects UV
Mike Kernaghan is chief executive of the Cancer Society of New Zealand
The Australian randomised control trial involved 1621 residents of a Queensland township who for four years in the 1990s were randomly assigned to either daily OR discretionary sunscreen application to head and arms (in combination with 30 mg beta carotene or placebo supplements) until 1996 and were observed until 2006. Ten years after the trial ceased 11 new melanomas had been identified in the daily sunscreen group and 22 in the discretionary sunscreen use group. The study concluded that melanoma may be preventable by regular sunscreen use in adults.
Green A, Williams G et al (2011) Reduced Melanoma After Regular Sunscreen Use: Randomized Trial Follow-Up, Journal of Clinical Oncology 29 (3)
The study examined data from the Norwegian Women and Cancer Study involving 143,844 women aged 40 to 75 years at start of study of whom 722 had had cases of melanoma. The study looked at the association between never using sunscreen, using sunscreen with a sun protection factor (SPF) of less than 15 and using a sunscreen with an SPF equal or greater to 15. It found that sunscreen users reported significantly more sunburns and sunbathing vacations and were more likely to use indoor tanning devices. It also found that using a sunscreen of SPF 15 or greater was associated “with significantly decreased melanoma risk” compared with using a sunscreen of less than SPF 15. It also concluded that if all women aged 40 to 75 used an SPF 15 or greater sunscreen they could potentially reduce their melanoma incidence by 18 per cent.
Ghiasvand 4, Weiderpass E, Green A et al (2016) Sunscreen Use and Subsequent Melanoma Risk: A Population-Based Cohort Study. Journal of Clinical Oncology 34 (33)