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DIRECT LINK BETWEEN UVB LIGHT AND MELANOMA ESTABLISHED
NEW YORK, NY (April 29, 1998) -- In a groundbreaking study, the first direct cause and effect relationship between ultraviolet light and the development of melanoma was established according to research presented at the American Academy of Dermatology's Melanoma/Skin Cancer Detection and Prevention Month press conference on April 29.
"What we set out to find is whether or not UV causes skin cancer," explained the lead author of the study Ercem Atillasoy, M.D., of the Wistar Institute and the Department of Dermatology at Thomas Jefferson University. "We developed a unique model for the study that used donated human newborn foreskin, which had never been exposed to sun in any way prior to the research." Using donated human newborn foreskin grafted on immunodeficient mice, three different treatments were completed, with one control group receiving no treatments. The first used a single treatment of DMBA. The second treatment used UVB irradiation (at 500 J/m2) three times per week. The third treatment combined UVB irradiation and DMBA. After a median of 10 months of treatment, the development of abnormal lesions including malignant melanoma was recorded.
The results of the study are published in the May issue of the American Journal of Pathology. The research found that out of 150 human foreskin grafts, 23% of the grafts treated with only UVB, and 38% of grafts treated with the combination of a chemical skin accelerant known as DMBA (7,12-dimethyl[a]benzanthracene) and UVB, developed abnormal pigmented lesions within 5-10 months of exposure. In one skin graft, in the third treatment group, a small, dark tumor - a melanoma - developed after 15 months of UVB and DBMA. The length of the UVB treatments equaled the amount of sun that would cause redness on an average Caucasian person's exposed skin. The treatments were administered at the same strength throughout the study.
"The newborn foreskin graft model is the first experimental system to yield a human malignant melanoma without any pre-existing sun exposure," said Dr. Atillasoy. "It provides evidence that UVB , as found in sunlight, is related to the evolution of malignant melanoma." The lack of pre-existing sun exposure also provided support for the theory that additional factors, such as genetic susceptibility, account for melanoma development in humans. Dr. Atillasoy noted that each of the test groups received the same strength and number treatments. The only variable that the researchers could not control was the genetic makeup found in the skin itself. The researchers theorize that the development of skin cancer may be linked to a combination of genetic susceptibility and UV exposure.
The lifetime incidence of melanoma in Caucasian Americans is approximately 1 in 70 (1.4%). The incidence of melanoma in the study in the third treatment group was 1 in 49 (2.1%). If left to develop indefinitely, the actual incidence may have been higher because the median period of observation was 10 months. The melanoma tumor developed in a graft 15 months after the beginning of treatment and 3 months after end of UVB exposure. The lifespan of these grafted mice is less than two years.
"There should be no controversy surrounding the effectiveness of sunscreen and sun protection methods in preventing skin cancer. We now have the first clear evidence that UVB exposure is directly linked to the development of melanoma," said Dr. Atillasoy. "The skin has a memory, upon which new sun damage builds. It is critical that people avoid the sun and use sun protection methods, such as sunscreen, every day."
The AAD is the world's largest organization of dermatologists representing 11,500 physicians that are experts in treating skin, hair, and nails.
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