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Scant Evidence that UV Exposure Causes Melanoma in Dark Skin Types
Researchers call for higher quality studies to understand the link between UV exposure and risk of melanoma for people with skin of color.
The Challenge
Melanoma is a potentially deadly type of skin cancer. Its incidence has increased dramatically over time, especially among people with fair skin. Incidence is much lower among people with skin of color.
Although rare, when melanoma occurs on dark skins, it’s often not diagnosed until it’s at a later stage, which leads to lower survival rates. This disparity in survival is why there’s increasing interest in understanding how to prevent melanoma in people with skin of color.
Researchers have provided evidence that supports that melanoma on the skin in people with fair skin is linked with their exposure to ultraviolet (UV) rays—like those from the sun and tanning beds. But there’s less evidence about the risk of UV exposure for people with skin of color.
Still, several skin cancer organization’s guidelines, including the American Academy of Dermatology, recommend UV protection for skin cancer prevention, including melanoma prevention in skin of color.
The Research
Before receiving his grant from the American Cancer Society, clinician scientist, Adewole S. Adamson, MD, MPP, and fellow researchers reviewed a large number of studies about skin color, UV exposure, and the risk of developing melanoma on the skin. They were looking for evidence that sunscreen would help protect dark skins from melanoma.
Research funded by the American Cancer Society has enabled my lab to take one step closer to precision medicine for this potentially devastating disease. We can identify the molecular features that make skin lymphomas more dangerous. The goal now is to identify novel drugs to target this aggressive disease subtype.”
He worked with his team to assess 548 full-text articles and found 13 studies met their needs. Those studies included a total of over 7,700 melanomas in people with skin of color across diverse racial and ethnic populations.
They found only 1 study with a small, statistically significant link between UV exposure and melanoma in Black people—but only Black men. Another single study found a significant link for Hispanic men. The other 11 studies showed no link between UV exposure and melanoma in skin of color in people in Asia and North America.
Thus, the authors say, current recommendations promoting UV protection, like wearing sunscreen, for to help prevent melanoma in people with skin of color are not supported by current studies.
Adamson and his coauthors noted several issues that decreased the quality of the studies. They didn’t account for the fact that people with skin of color have a wide range of melanin concentrations—higher levels/darker skin helps protect the skin from UV light. Nor did the studies differentiate between melanoma subtypes, like acral melanoma, the most common type of melanoma in people with skin of color.
The authors note, though, that sun protection can still be beneficial for people with skin of color. For instance, sun screen can help reduce sunburn, wrinkles, premature aging caused from the sun (photoaging), and dark spots on the skin (melasma and postinflammatory hyperpigmentation). And as Adamson learned from an ACS-funded grant, sun screen can help reduce non-melanoma types of skin cancer in East Asian individuals.
It’s also important for people with dark skin to use sun protection if they have had an organ transplant, are immunosuppressed, or have a history of xeroderma pigmentosum, a rare condition passed down through families that causes the skin and tissue covering the eye to be extremely sensitive to UV light.
Why It Matters
The risk factors for developing acral melanoma are not understood. To learn more about the risk factors of melanoma for people with skin of color, more studies need to include people who have skin of color and have objective ways to quantify their risk. For instance, most the studies Adamson reviewed only included race and ethnicity, which may not accurately link with the amount of melanin in the skin or the likelihood of developing a sunburn.
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