The report in the Dec. 21 issue of the Journal of the National Cancer Institute also indicates that only nonmelanoma skin cancers (i.e., basal and squamous cell carcinomas) are strongly associated with exposure to UVB radiation.
That does not mean, however, that sunbathing poses a minimal risk of developing melanoma. Researchers say that ultraviolet A (UVA) radiation, the rays in sunlight that reach the deeper layers of skin and are associated with signs of aging, can damage the DNA in melanocytes, the pigment-producing cells that give rise to melanoma.
Although we have refined the common wisdom that excess sun exposure is always associated with increased risk of skin cancer, the take-home message for the public is still the same − limit sun exposure and use a sunscreen that blocks both UVA and UVB rays, says the studys lead investigator, Qingyi Wei, M.D., Ph.D., professor in the Department of Epidemiology.
The study is a painstaking analysis of the ability of UVB radiation to damage a cells chromosomes. Chromosomal injury is one way cells can become cancerous; damage to the genes that make up the chromosome is another, and Wei and his colleagues already have shown in previous studies that melanoma patients often have a reduced capacity to repair the DNA damage that results from UV exposure.
In the novel study, researchers looked at how often chromosomes break in cells from skin cancer patients compared with cells from a control group.
Wei and his team of 16 collaborators at M. D. Anderson gathered white blood cells from 469 skin cancer patients treated at M. D. Anderson (238 of whom were diagnosed with melanoma) as well
Contact: Stephanie Dedeaux
University of Texas M. D. Anderson Cancer Center