Public Health and the Tanning Bed Controversy

Abstract

In this issue of Journal of Clinical Oncology, Zhang et al provide further evidence of the harmful effects of indoor tanning, particularly in the young. They studied a cohort of women who participated in the Nurses’ Health Study (II). This included more than 70,000 women monitored for 20 years, and the investigators asked whether indoor tanning during youth increased the risk of skin cancer, specifically basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and invasive melanoma. They reported an increased risk for all three tumors, particularly BCC, independently associated with tanning bed use before age 35 years. The investigators controlled for confounding demographic factors, most importantly skin type, sun sensitivity, UV index of residence, and sun exposure behavior during youth. They also identified a doseresponse effect of indoor tanning, with more frequent use associated with an increased risk of BCC and SCC. In another recent study, Ferrucci et al reported a significant risk of early-onset BCC associated with indoor tanning in the young. They found a 69% increase in the risk of early-onset BCC in patients who reported prior tanning bed use compared with agematched controls with noncancer dermatologic conditions. In this large, well-conducted study, the population-attributable risk of BCC in women younger than 40 years could be reduced by an estimated 43% by avoiding indoor tanning. These data confirm the observations made by Zhang et al and identify the particular hazard associated with indoor tanning in the young, as well as the strong association of indoor tanning with skin cancer, particularly BCC. These data come as no surprise to the melanoma community, long concerned about the hazards of voluntary UV exposure in the form of tanning salons. The increased risk of BCC associated with indoor tanning by the young in both of these studies is compelling. Melanoma risk was also increased with the use of indoor tanning in the study by Zhang et al, although the association was weaker and there was no dose-response relationship observed. Other investigators have reported an increased risk of melanoma in indoor tanners, especially when tanning beds are used before age 35 years (summary relative risk 1.75; 95% CI, 1.35 to 2.26). In a casecontrol study in Sweden, Westerdahl et al reported a significant elevation in risk of melanoma associated with ever having used a tanning device (OR 1.3; 95% CI, 0.9 to 1.8) which was even higher when those younger than 30 years were considered (OR 2.7; 95% CI, 0.7 to 2.8). This effect was observed after adjusting for patient factors and sun exposure history. The relationship between UV radiation, DNA damage, and skin cancer is not exactly headline news, yet approximately 30 million Americans use tanning salons at least once a year. Women and young people are the most frequent users. In Northern Europe, more than 60% of women and 50% of men reported using indoor tanning equipment in the 1990s. For these individuals, the perceived benefits of indoor tanning appeared to outweigh the well-known risks of premature aging of the skin, skin cancer, and immunosuppression. Indoor tanning is one of the most rapidly growing industries nationally, with a three-fold increase in the number of indoor tanners in the United States between 1986 and 1996. The tanning bed industry has responded to safety concerns raised by public and private organizations by taking the offensive (the best defense) and promoting indoor tanning as “healthy.” The tanning industry uses terminology such as “safe tanning” and promotes the positive effects of UV irradiation on vitamin D production to refute the claims of those concerned about cancer risk. Although UV exposure does increase dermal production of vitamin D, it is difficult to argue that exposure to excessive levels makes sense when a dietary supplement, healthy diet, and/or limited sun exposure can address vitamin D deficiency or maintain adequate levels without an associated hazard. In addition, most modern tanning devices emit primarily UVA, which is relatively ineffective in promoting vitamin D synthesis. Both UVA and UVB rays are emitted by lamps in tanning beds, and both are carcinogenic. UVB (wavelength, 290-320 nm) penetrates the top layers of skin and is the type of UV radiation associated with sunburns. Most sunscreens block UVB. UVA (wavelength, 320400 nm) affects the deeper layers and is the major UV component in sunlight and tanning beds, perhaps because it is associated with immediate tanning. UVA is blocked only by “full-spectrum” sunscreens, more commonly available in Europe than the United States. Both forms of UV radiation can damage the eyes, and protective eyewear is essential to decrease this risk. The tanning mechanism requires DNA damage. DNA damage leads to activation of p53 in keratinocytes and subsequent induction of transcription of pro-opiomelanocortin and proinflammatory cytokines. Alpha melanocyte–stimulating hormone, a cleavage product of pro-opiomelanocortin, signals melanocytes via the melanocortin 1 receptor, with subsequent melanogenesis, differentiation of melanocytes, and transfer of melanin to keratinocytes via melanosomes, which results in tanning. No DNA damage, no tan. An interesting by-product of activation of this pathway is release of -endorphin, which may explain the positive effects on mood of UV irradiation and sun/UV–seeking behavior. UV radiation is JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 30 NUMBER 14 MAY 1