Sun exposure may have benefits
Sunlight exposure, a major risk factor for the potentially deadly skin cancer melanoma, may also help victims survive that disease, new research indicates.
And a second study indicates that exposure to sunlight may reduce the risk of getting cancer of the lymph glands.
“Sunlight, particularly ultraviolet radiation, is a very well established human carcinogen. Nothing in these papers should in any way detract from this message,” said Kathleen M. Egan of Vanderbilt University Medical Center.
But the new reports, published in the current issue of the Journal of the National Cancer Institute, do provide important clues to the development of these cancers and some factors that may slow or stop them.
Melanoma has been increasing over the last half-century in developed countries with white populations, and studies have consistently found exposure to the sun a major risk factor.
However, a new look at 528 melanoma victims over five years also found that increased sun exposure led to increased survivability, according to the study led by Marianne Berwick of the department of internal medicine at the University of New Mexico.
“It’s totally counterintuitive, and we’re trying to investigate it,” said Berwick, noting that she is now doing a study of 3,700 melanoma patients worldwide.
“It’s really strange, because sunburn seems to be one of the factors associated with improved survival, and that doesn’t make much sense, so we think sunburn’s a proxy for the kind of sun exposure that leads to melanoma,” Berwick said.
She said vitamin D, which the skin makes in response to sunlight, may be a factor. Vitamin D can regulate cell growth and help cells stop unneeded growth by a process called apoptosis.
Another possibility is solar elastosis, a response to sunlight that breaks down collagen in the skin -- the same process that causes sun-related wrinkling. “It may be that some physical barrier created by this breakdown of collagen keeps the melanoma from getting into the blood and lymph system,” Berwick said.
In the second study, researchers in Stockholm, Sweden, studied 3,000 lymph cancer patients and a similar number of people without lymph cancer in Denmark and Sweden.
They found that increased exposure to ultraviolet through sunbathing and sunburns resulted in a reduced incidence of non-Hodgkin’s lymphoma.
Vanderbilt’s Egan, who was not involved in either research team, said it’s unlikely to be sunlight itself that is an explanation for the findings. The scientific community is converging on the idea that vitamin D is likely to be a protective agent, she said.
