Frequent use of indoor tanning beds significantly increased the risk of users developing a second primary melanoma compared with non-users, and they did so far more quickly than non-users, according to a retrospective study.
In an analysis involving 434 patients with melanoma, 56% of patients exposed to artificial ultraviolet radiation (arUVR) were diagnosed with a second primary melanoma within 1 year of their first diagnosis compared with 18% of patients who had not been exposed to arUVR (P=0.011), reported Lynn Cornelius, MD, of the Washington University School of Medicine in St. Louis, and colleagues.
The median time to diagnosis of the second primary melanoma was 225 days in patients who had been exposed to arUVR compared with 3.5 years for those who had not (P=0.027), they wrote in the Journal of the American Academy of Dermatology.
“Tanning beds expose persons to arUVR with intensities up to 10X that of natural sunlight,” they stated. “This study highlights the need for patient education regarding the risks of artificial tanning and the importance of vigilant surveillance for melanoma recurrence and additional primary melanomas.”
Patients were seen at a multidisciplinary melanoma clinic at the authors’ institution, and were asked to complete a melanoma patient questionnaire that included questions on sun exposure and photoprotection measures. In a later version of the questionnaire, investigators also asked patients how many hours they estimated they had been exposed to arUVR: either 1 to 50 hours or >50 hours.
Of the 434 patients included in the analysis, 131 were ages ≤40 years of and 303 were ages >40. Over three-quarters of patients in the younger cohort were female (P<0.0001).
More women (82%) reported being exposed to arUVR than men (18%), and reported ever using a tanning bed (P<0.0001). Age also factored into tanning bed use such that the likelihood an individual would be exposed to arUVR from tanning beds dropped by about 16% with each 5-year increase in age.
Also, 42% of patients in the younger cohort reported they had used a tanning bed at some point in their lifetime versus 17% of patients ages >40 (P<0.0001). Patients ages ≤40 were also more likely to report high levels of arUVR exposure than older patients, with some 29% of the younger cohort reporting a lifetime exposure to arUVR of either >50 hours or >100 hours compared with only 9% of patients ages >40.
“Overall, the probability of tanning bed use was highest among patients with melanoma diagnoses at earlier ages (40 or younger), but the rising trend persisted in all … age categories,” they stated.
For example, when adjusted for age, sex, race, and melanoma stage, the odds that participants had been exposed to arUVR from tanning beds increased by 48% for each additional primary melanoma diagnosed. However, tanning bed users reported that they were more likely to use sunscreen (73% versus 57% for nonusers), and most reported using sunscreen always or most of the time (P=0.0093).
This might be explained by the fact that many tanning beds users apparently believe that indoor tanning is safer than outdoor tanning, and thus are more likely to apply sunscreen when exposed to natural sunlight.
“Our study is the first to demonstrate that regardless of age, patients who had second primary melanoma diagnoses were more likely to have had arUVR exposure,” the investigators stated.
They also suggested that because patients in the study who used tanning beds were more likely to be fair-skinned than non-users, “the increased arUVR intensity of tanning beds, as opposed to UVR from ambient sunlight in a physiologically vulnerable patient population (fair skinned persons) at an early age contributes to our findings of decreased tumor lag time.”
Study limitations included the fact that it was carried out in a single geographic area, and with a relatively small sample size.
Marc Glashofer, MD, of The Dermatology Group in West Orange, New Jersey, noted that the actual cause of melanoma is still being worked out because some melanomas can occur on non sun-exposed areas of the skin, suggesting that genetic factors may be at play as well as UVR exposure.
Nevertheless, tanning bed use is a strong driver of melanoma risk, as there is still a strong cultural drive for young, fair-skinned females, to arrive at a big social event sporting a deep tan, for which they have spent expensive sessions in a tanning salon acquiring.
“Even with us having more data on the carcinogenic effects of excessive UVR — even with that message being out there — you are dealing with patients in their late teens and early 20s who still have that, “I’m going to live forever mentality,'” Glashofer, who was not involved in the study, observed.
He noted that dermatologists have long been making an effort to promote “paleness” as the new beauty standard, but “this is a really tough cultural shift to make because people still believe they look better when they are tanned.”
Glashofer said he tells his young tanning bed users that they are actually paying to get cancer by exposing themselves to arUVR. “The message gets through to some, but not everyone,” he said.
However, the message seems to be getting through to state legislators, as some states have been progressively moving towards raising the age of consent to permit tanning bed use. But the tanning bed industry has a strong lobby who are actively trying to dissuade the same state legislators from restricting tanning bed use, he pointed out.
The study was funded by REDCap and the National Cancer Institute Cancer Center.
Cornelius and co-authors, as well as Glashofer, disclosed no relevant relationships with industry.