Skin Cancer Rare -- But More Deadly -- In People With Darker Skin

Hugh Gloster, MD, associate professor of dermatology at UC, says that dark-skinned people--including blacks, Asians, Hispanics and Native Americans--develop fewer nonmelanoma skin cancers compared with whites. But when the disease does occur, it is typically more aggressive and diagnosed in its later stages, which leads to disproportionately more deaths among minority populations.

This research was presented today (July 27) at the summer meeting of the American Academy of Dermatology in San Diego, Ca.

"There's a perception that people with darker skin don't have to worry about skin cancer, but that's not true," explains Gloster, lead author of the study. "Minorities do get skin cancer, and because of this false perception most cases aren't diagnosed until they are more advanced and difficult to treat."

"Unfortunately," he adds, "that translates into higher mortality rates."

Skin pigmentation cells, known as "melanocytes," produce a chemical called melanin that gives the skin color and helps block out damaging ultraviolet (UV) rays from the sun and artificial light sources like tanning beds. Dark-skinned people produce more melanin in the skin, and are therefore less susceptible to severe skin "burn" and UV damage.

Dark skin has increased epidermal melanin, explains Gloster, which provides a natural skin protection factor (SPF) of more than 13 in dark-skinned blacks, and filters twice as much UV radiation as white skin, which has far less melanin.

Gloster and his UC colleague Kenneth Neal, MD, conducted a retrospective review of clinical data collected over the last 50 years by medical centers across North America, Asia and Africa to determine which epidemiologic and medical features of skin cancer are unique to dark skin.

They determined that while incidence rates of basal and squamous cell carcinomas and melanomas among whites have increased between 5 and 8 percent, rates among blacks for the same period remained relatively constant. More important, although fewer blacks developed skin cancer, a larger number of them died of the disease, Gloster says.

In addition, UC researchers noted that blacks were 8.5 times more likely to develop squamous cell carcinoma--which occurs in the upper layers of the skin and is the second most common type of skin cancer--on areas protected from to the sun (hand palms, toes and mucous membranes) than those areas of the body that are regularly exposed to the sun (the nose, ears and backs of the hands).

This, the researchers say, implies that UV radiation does not play as important a role in the development of squamous cell carcinoma in minorities as it does in whites.

Gloster says physicians should stress behavior modifications, including regular use of sunscreen and self skin checks for significant changes in moles and skin texture, with all their patients.

"It's especially important that physicians stress these messages with young women," he adds. "Dermatologists are seeing an increased number of skin cancer cases in women under 30--and most are either former tanning bed users or people who don't regularly use sunscreen."

Melanoma, the most aggressive form of skin cancer, appears to develop differently in whites than in darker-skinned people in whom the disease usually appears on the palms, soles, and under the nails. This data suggests that UV radiation is not a significant risk factor for melanoma in dark ethnic groups. However, UV radiation is considered a chief cause of the disease in whites--specifically from intense early-life and blistering sunburns

According to the U.S. Census Bureau, 50 percent of the U.S. population will be black, Asian or Hispanic by the year 2050, which reinforces the importance of early detection and awareness among this population.

"We need to increase public awareness of skin cancer among ethnic minorities if we're going to decrease skin cancer-related deaths," adds Gloster. "Prevention is key to fighting this disease."

The American Cancer Society estimates that more than 68,700 people will develop skin cancer in 2006--about 90 percent of them getting the most serious type, melanoma.

This study was sponsored by the UC dermatology department.