The relationship between melanoma, the most dangerous form of skin cancer, and sunburn was the focus of an article in the April 29, 1999, issue of The New England Journal of Medicine, by Barbara A. Gilchrest, MD, Mark S. Eller, PhD, Alan C. Geller, RN, MPH, and Mina Yaar, MD, all of the Department of Dermatology at Boston University.

The study found the risk of melanoma, the most deadly type of skin cancer, rises directly with the number of sunburns we suffer.

Skin cancer is the most common of all cancers and is divided into two general types:

• Non-melanoma skin cancers, chiefly basal cell and squamous cell cancers, are the most common forms of the disease. They are called non-melanoma because they develop from skin cells other than melanocytes, like keratinocytes, the outer skin cells that synthesize keratin, a fibrous protein that forms the outermost barrier layer of skin, as well as hair and nails. Non-melanoma cancers occur most often after years of frequent UV exposure, like that received by farmers, sailors, and others who spend much of their time outdoors.
• Melanoma, in contrast, is a cancer that begins in the melanocytes, those deeper skin cells that produce the skin coloring known as melanin. After sun exposure, melanin is released to protect the skin, giving it the darker coloring known as a suntan.

"Nature has provided the body with effective photoprotection in the form of melanin, which directly absorbs ultraviolet photons," said Dr. Gilchrest. Tanning happens when the deeper skin cells react to injury posed by UV radiation and transfer more melanin to the surrounding outer skin cells. This protective response by the skin acts as a natural sunscreen, with a measured sun protection factor (SPF) of three to five.

Because the outer cells are closer to the surface and thus more vulnerable to the sun, they quickly undergo a process called apoptosis, or programmed cell death, which eliminates cells with damaged DNA. The cells are eventually shed from the skin.

The deeper cells, or melanocytes, respond to sun exposure quite differently. The typical sunburn, which occurs with prolonged exposure to the sun after a period of avoiding it, will substantially damage the DNA of the melanocytes located deeper in the skin. Research shows melanocytes are highly resistant to programmed cell death. "This is perhaps nature?s way of assuring the continued presence of protective melanin pigment in the skin," explained Dr. Gilchrest.

This resistance to cell death enables UV-damaged melanocytes to mutate and divide, increasing the risk of melanoma with each sunburn. The study suggests a history of five or more severe sunburns during adolescence more than doubles the risk of getting melanoma later in life.

Although highly curable if detected in its earliest stages, like basal cell and squamous cell skin cancers, melanoma is much more likely to spread to other parts of the body. Melanoma accounts for about four percent of all skin cancer cases, but causes about 79 percent of skin cancer deaths.

"Protection from the sun is critical to the prevention of both melanoma and non- melanoma skin cancers, and protection is most effective when it is begun early in childhood," the study warns. Experts estimate the average adult may have received up to 80 percent of their lifetime UV exposure by the age of 18.

However, the use of sunscreen only plays a part in protecting the skin against UV damage. There must also be a change in how people protect themselves from the sun.

Because melanomas are associated with more intense and infrequent sun exposure, people who work indoors and whose sun exposure is limited to weekends and vacations are at greater risk, possibly because more people are traveling long distances to sun- intense places during the winter.

"Until sun-seeking behavior is deglamorized over time, melanoma and other skin cancer rates will continue to increase," said Martin Weinstock, MD, PhD, director of the Dermatoepidemiology Unit at Brown University and chairman of the American Cancer Society?s (ACS) Skin Cancer Advisory Board. "There has been a transformation of society in the last hundred years or so, from a time when sun protection was a priority, to now, when sun exposure has become a goal for many. Once a tan ceases to be glamorized, skin cancer rates will begin to fall."

Joseph Dye, RPh, PhD, a behavioral scientist at the ACS, agreed that in order to reduce the rate of skin cancer, we have to change the intensity of our exposure to the sun. Offering insight into unhealthy sun habits, he added, "Another possible factor is that too many people, especially those with fairer skin, are misusing sunscreen. By mistakenly believing they can apply sunscreen and then stay outside all day, they may be exceeding the limits to which their skin can defend itself against the sun."

Protection equals prevention, when it is done correctly. Try to avoid outside activities between 10 a.m. and 4 p.m., and be sure to wear tightly woven, light-colored clothing, a hat with at least a 4-inch brim brim, and a liberal amount of sunscreen with at least an SPF 15.

The American Cancer Society (ACS) estimates about 44,200 new cases of melanoma will be diagnosed in the US in 1999, and about 7,300 people will die of the disease.

• Melanoma Skin Cancer
• Sunlight and Ultraviolet Radiation
• Prompt Action Improves Survival Rate for Melanoma Patients
• New Melanoma Test
• TA-90 Marker for Skin Cancer