CORRESPONDENCE

RESPONSE: More About: Sunscreen Use, Wearing Clothes, and Number of Nevi in 6- to 7-Year-Old European Children

Philippe Autier, Jean-Francois Doré, Gianluca Severi, For The European Organization for Research and Treatment of Cancer Melanoma Cooperative Group

Affiliations of authors: P. Autier, G. Severi, European Institute of Oncology, Milan, Italy; J.-F. Doré, Institut National de la Santé et de la Recherche Médicale, Centre Léon Bérard, Lyon, France.

Correspondence to: Philippe Autier, M.D., Division of Epidemiology and Biostatistics, European Institute of Oncology, Via Ripamonti 435, Milan 20141, Italy (e-mail: pautier{at}ieo.it).

The new analysis of the Western Canada Melanoma Study is consistent with the absence of a direct hazardous effect of sunscreens. Likewise, data from our study (1) do not suggest a direct effect of sunscreens on development of nevi. Data in Table 2 of our published article (1) indicate that it is not sunscreen use that has a direct effect on development of nevi, but rather it is the sun. And data in Table 3 of our published article (1) suggest that the role of sunscreen use is probably to allow amounts of sun exposure that would not be possible otherwise. The latter mechanism, however, still needs confirmation.

Other aspects of our study are against a direct effect of sunscreen use on the occurrence of nevi or melanoma. In all four countries where our study was conducted, the number of nevi tended to increase with increasing sunscreen use and to decrease with the wearing of clothes (1). In contrast, mothers reported using more than 100 different brand names of sunscreens—on their children, and many sunscreen formulations found in one country were not available in another country.

Drs. Elwood and Gallagher interpret their data as being the result of sunscreens' providing incomplete protection against the effects of excess intermittent sun exposure. But the suggestion of incomplete protection implies that sunscreen use would in any event confer some protection. In that logic, after appropriate adjustment, a higher melanoma risk should be found when sunscreen is never or rarely used, mainly among subjects with high levels of intermittent sun exposure. We see no evidence in this new analysis for a protective effect of sunscreen use, even among subjects who "always" used sunscreen. Also, in our data (1,2) on subjects having high levels of intermittent sun exposure, sunscreen use was associated with higher melanoma risk or higher number of nevi (1,2).

Drs. Elwood and Gallagher state that to date no study has assessed the protection conferred by newer broad-spectrum sunscreens, mainly those containing effective ultraviolet-A-blocking chemicals. Actually, most sunscreens used by the children in our study (1) were broad-spectrum sunscreens, containing effective ultraviolet-A filters. The eventual role of ultraviolet A in the development of human melanoma remains largely unknown. But the suggestion that ultraviolet-A would be involved in the melanoma-sunscreen association implies that, although the sunscreen blocks ultraviolet-B (and thus retards sunburn occurrence), greater amounts of ultraviolet-A reach the skin cells than in the absence of sunscreen. This occurrence can be achieved only if sunscreen use allows sun exposures of longer duration.

Another hypothesis is possible. For instance, a given dose of ultraviolet is a more efficient carcinogen when delivered in multiple fractions or over a longer period of time (3). From these data, one could argue that sunscreen use could modify the way ultraviolet-B is delivered to skin cells, resulting in greater carcinogenic efficiency.

Hence, studies are still needed to elucidate the precise mechanism by which sunscreen, when used for recreational or cosmetic sun exposure, would increase melanoma occurrence.

REFERENCES

1 Autier P, Dore JF, Cattaruzza MS, Renard F, Luther H, Gentiloni-Silveij E, et al. Sunscreen use, wearing clothes, and number of nevi in 6- to 7-year-old European children. J Natl Cancer Inst 1998;90:1873-80.[Abstract/Free Full Text]

2 Autier P, Dore JF, Schifflers E, Cesarini JP, Bollaerts A, Koelmel KF, et al. Melanoma and use of sunscreens: an EORTC case-control study in Germany, Belgium and France. The EORTC Melanoma Cooperative Group. Int J Cancer 1995;61:749-55.[Medline]

3 IARC monographs on the evaluation of carcinogenic risks to humans. Solar and ultraviolet radiation. Vol 55. Lyon (France): International Agency for Research on Cancer; 1992. p. 139-161.



             
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