SPF30 sunscreen may protect against melanoma skin cancer, a new study finds.
Principal Investigator Christin Burd, of the Comprehensive Cancer Center at Ohio State University, and colleagues reached their conclusion by testing sunscreen on a genetically engineered mouse model of melanoma.
While their results may appear obvious at first glance, the study authors point out that previous research has only been able to test whether sunscreen use protects against sunburn, not whether it protects against cancer.
"Sunscreens are known to prevent skin from burning when exposed to UV [ultraviolet] sunlight, which is a major risk factor for melanoma," notes Burd.
"However, it has not been possible to test whether sunscreens prevent melanoma, because these are generally manufactured as cosmetics and tested in human volunteers or synthetic skin models."
In a previous study, Burd and colleagues revealed how they developed a mouse model that is genetically engineered to spontaneously develop melanoma around 26 weeks after skin application of the chemical 4-hydroxytamoxifen (4OHT).
SPF30 sunscreen delayed melanoma onset, reduced tumor incidence
For this latest study, the team exposed the melanoma mouse models to UVB radiation, which is the primary cause of sunburn. UVB radiation tends to damage the epidermis - the outer layers of skin.
One day after applying 4OHT to the skin of the mice, the researchers exposed the rodents to a single dose of UVB radiation. They found this accelerated melanoma progression and the mice developed significantly more tumors.
"Melanoma-free survival was reduced by 80%, to about 5 weeks," notes Burd.
Next, the researchers applied a variety of SPF30 (sun protection factor 30) sunscreens - all of which contained a number of UV-blocking agents - to the skin of melanoma mouse models prior to UVB exposure.
Every sunscreen applied was found to delay melanoma onset and reduce tumor development, though there were some minor differences in the melanoma-preventing abilities of each product.
"However, we later discovered that even though the sunscreens were all marketed as SPF30, some were actually predicted to have a higher rating," says Burd. "For this reason, it is hard to compare the melanoma-preventing capacity of the different sunscreens at this time."
Mouse model could be used to identify new melanoma-prevention agents
The authors point out that they only tested the effect of SPF30 sunscreens against a short dose of UVB radiation - the equivalent to the amount of UVB a person is likely to be exposed to during a week-long beach vacation - which is a major study limitation.
- Around 76,380 new cases of melanoma will be diagnosed in the US this year
- More than 10,000 Americans will die from the disease
- Rates of melanoma in the US have been rising for the past 30 years.
"Sunscreens were never meant to handle a week's worth of sun given at one time, and we are working to reduce the UVB dose we use in our studies," Burd notes.
Furthermore, the team only exposed the mouse model to UVB light, so they are unable to say whether SPF30 sunscreens may delay melanoma onset following exposure to UVA radiation and other wavelengths of sunlight.
The researchers are currently seeking funding to address this research gap using their mouse model, but they note that securing such funding proves challenging; most sunscreens are developed by the cosmetic industry, which has vowed to avoid animal testing.
Still, the authors say their current study represents the first in vivo model that can be used to test the efficacy of sunscreen for melanoma prevention.
What is more, they believe their model can be used to identify and test new, more effective agents that could help protect against melanoma.
"We have developed a mouse model that allows us to test the ability of a sunscreen to not only prevent burns but also to prevent melanoma. This is a remarkable accomplishment. We hope that this model will lead to breakthroughs in melanoma prevention."
Medical News Today recently reported on what SPF is and which sunscreen is best to use.