Consistent use of sunscreen during childhood and infancy, according to a new study, is essential to preventing melanoma in adulthood.
Malignant melanoma is the most aggressive form of skin cancer - the American Cancer Society estimates that more than 75,000 new cases of melanoma will be diagnosed in the United States this year.
And despite the increased use of sunscreen in the last several decades, skin cancer is still the most common form of cancer in the country, according to the US Centers for Disease Control and Prevention.
"While sunscreen is highly effective in preventing sunburn, this paradox has led some to question whether sunscreen is effective in preventing melanoma caused by ultraviolet (UV) light," senior author John L. VandeBerg said in a statement.
"It has been suggested that sunscreen enables people to receive more UV exposure without becoming sunburned, and that increased exposure to UV light has led to an increasing incidence of melanoma."
Questions regarding the effectiveness of sunscreen have remained unanswered in part because, until recently, no natural mammalian model of UV-induced melanoma has existed, VandeBerg noted.
Scientists at Texas Biomedical Research Institute have established the gray short-tailed opossum as such a model. They tested an over-the-counter facial lotion containing SPF15 sunscreen on this South American marsupial, assessing for its ability to prevent UV-induced melanoma.
The use of sunscreen-containing lotion resulted in a 10-fold reduction in pre-melanotic lesions, known to progress to melanoma. That's compared to opossum infants who did not wear lotion with sunscreen.
Researchers monitored these animals into adulthood, which is when melanomas appeared, just like in humans.
"We speculate that the reason it is particularly important that sunscreens be used consistently in childhood, and especially in infancy, is because skin cells during growth are dividing much more rapidly than in adulthood, and it is during cell division that the cells are most susceptible to UV-induced damage," VandeBerg concluded.
The study was published in the latest issue of Pigment Cell and Melanoma.