New Research Shows Cancer Prevalent in Darker Skin
Published August 2006
“You’re not immune to skin cancer.”
That’s the simple message UC dermatologist Hugh Gloster, MD, wants people with dark skin—including blacks, Asians, Hispanics and Native Americans—to take seriously this summer.
Although dark-skinned people develop fewer nonmelanoma skin cancers compared with whites, he says, when the disease does occur, it’s typically diagnosed late. Andthat leads to disproportionately more deaths among minority populations.
“There’s a perception that darkskinned people don’t have to worry about skin cancer, but that’s absolutely not true,” explains Gloster, an associate professor of dermatology.
“Dark-skinned people do get skin cancer, and because of this false perception most cases aren’t diagnosed until they are in more advanced—and difficult to treat—stages.
“Unfortunately,” he adds, “that translates into higher mortality rates.”
Skin pigmentation cells, known as “melanocytes,” produce a chemical called melanin that gives the skin its color and helps block out damaging rays from the sun.
Darkskinned people produce more melanin in the skin, so they are less vulnerable to severe skin “burn” and damage from ultraviolet (UV) radiation. This electromagnetic radiation is emitted from the sun and some artificial light sources, including tanning beds.
“Because dark skin has increased epidermal melanin,”explains Gloster, “it provides a natural skin protection factor of about 13 in blacks and filters twice as much UV radiation as white skin, which has far less melanin.”
Gloster and his colleagues reviewed 50 years of clinical data from medical centers across North America, Asia and Africa to determine which epidemiologic and medical features of skin cancer are unique to dark skin.
They found that while rates of basal and squamous cell carcinoma and melanoma 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.In addition, blacks were 8.5 times more likely to develop squamous cell carcinoma—which occurs in the upper layers of the skin—on areas protected from the sun, such as the hand palms, toes and mucous membranes, than areas of the body that are regularly exposed to the sun, including the face, chest 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 blacks as it does in whites.
“Physicians should stress behavior modifications with all their patients, including regular use of sunscreen and checking their own skin for significant changes in moles and skin texture,” says Gloster.
“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.
About 50 percent of the U.S. population will be black, Asian or Hispanic by the year 2050, according to the U.S. Census Bureau, 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 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.