Patterns and timing of sunlight exposure play a role in developing skin cancers
Results of the first case-control study of the patterns and timing of sunlight exposure and how each is related to basal cell carcinoma and squamous cell carcinoma have been published in the open-access journal BioMed Central.
This study, conducted by researchers at Moffitt Cancer Center, the University of South Florida, and the International Agency for Research on Cancer in France, simultaneously evaluated identical patterns and timing of sunlight exposure as they are related to basal cell and squamous cell carcinomas in the same US population with high annual ultraviolet radiation exposure. The study included 703 Florida residents: 218 with basal cell carcinoma, 169 with squamous cell carcinoma, and 316 without skin cancer. The patterns of sunlight exposure studied were continuous or intermittent, and the timing refers to sun exposure during childhood, adulthood, or both.
“There are more than a million new cases of basal cell and squamous cell carcinomas diagnosed in the United States each year,” said senior study author Dana E. Rollison, PhD, associate member of the Cancer Epidemiology Program, and vice president and chief health information officer at Moffitt. “While mortality associated with nonmelanoma skin cancers, such as basal cell and squamous cell carcinomas, is low, patients may experience substantial morbidity and treatment costs are high.”
Greater toxic sunlight exposure and the chances of receiving blistering sunburns are higher during childhood. In fact, it is estimated that 25% of lifetime sunlight exposure occurs before age 18.
“Blistering sunburn is believed to result from high doses of intense ultraviolet radiation exposure in short increments of time and is considered to be a measure of intermittent exposure,” said study coauthor Michelle Iannacone, Marie Curie postdoctoral fellow at the International Agency for Research on Cancer.
Specific patterns the researchers sought to identify and correlate to basal cell and squamous cell carcinomas included: 1) intermittent exposure to ultraviolet radiation, perhaps while on summer vacation in high ultraviolet radiation regions, and 2) continuous exposure through working at a job outside in the sunlight.
Study subjects were surveyed on their memory of past sun exposure.
According to survey results, a history of blistering sunburn is related to both basal cell and squamous cell carcinomas. Furthermore, an occupation requiring time in the sunlight was also associated with basal cell and squamous cell carcinomas. Sunlight exposure at a younger age “tended to be associated with squamous cell carcinoma, but not basal cell carcinoma, risk,” researchers concluded.
“Sunlight exposure, regardless of the exposure pattern, is associated with both basal cell and squamous cell carcinomas,” Iannacone said. “Understanding how sunlight exposure response may differ by nonmelanoma skin cancer type is important for educating the public on safe sunlight behaviors. Applying sunscreen while on vacation may decrease basal cell carcinoma risk with intermittent sunlight exposure, but may not impact the risk of squamous cell carcinoma, which may be more strongly related to continuous sunlight exposure.”
Source: Moffitt Cancer Center.