© 1999 by Oxford University Press
Journal of the National Cancer Institute, Vol. 91, No. 12, 1079-1080,
June 16, 1999
© 1999 Oxford University Press
CORRESPONDENCE |
RESPONSE: Re: Sunscreen Use, Wearing Clothes, and Number of Nevi in 6- to 7-Year-Old European Children
Affiliations of authors: P. Autier, 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).
In their letter, Gasparro and Berwick suggest that the increase in nevi number associated with sunscreen use that we observed in our study (1) is indicative of our general ignorance of the causal link that exists between sun exposure and nevi development or melanoma occurrence. We fully agree that this gap in our knowledge should be filled.
However, the link between sun exposure and melanoma could be more complex than just an issue of finding the relevant wavelength(s) responsible for nevi development. How ultraviolet radiation is delivered to the skin may also be of importance. For instance, it has been demonstrated that a given quantity of ultraviolet B radiation is more carcinogenic when administered in fractionated doses than in a few high doses or when doses are administered over a longer period of time (2).
Our data show that it is not sunscreen use that has a direct effect on nevi development, but the sun itself; sunscreen use probably allows higher amounts of sun exposure that would not be possible otherwise (1). Hence, sunscreen use would affect nevi development or melanoma risk more by a modification of the way wavelengths are delivered to the skin cells, rather than by a modification of wavelengths transmitted to the skin cells. In that respect, further work on the sunscreen-melanoma (or sunscreen-nevi) association could help to elucidate the mechanisms involved in the sunlight-melanoma association. Further research would also provide indications on how sunscreens should be formulated and used, for more efficient sun protection.
By discovering the nature of the sunlight-melanoma association, a constructive dialogue between basic and epidemiologic research could be very productive. Epidemiological data tell us that it is the "intermittent" sun exposure that is mainly associated with melanoma occurrence, not the so-called "chronic" sun exposure pattern (3). Sunburn experience at all ages is associated with melanoma occurrence (3). However, sunburns are considered more and more as markers of natural susceptibility to sunlight and excessive sun exposure, rather than direct causes of melanoma (4). This last statement does not mean that avoiding sunburn is unimportant. Rather, it stresses that avoidance of sunburn (e.g., by using a sunscreen) does not necessarily equate to preventing all carcinogenic effects of solar radiation. Thus, epidemiologic data suggest that future experiments should try to mimic the sun exposure patterns mostly associated with melanoma occurrence (for instance, by examining in more detail the biologic effects of repeated suberythemal doses of ultraviolet radiation).
In their turn, epidemiologic researchers should adopt techniques developed within the framework of laboratory experiments. To date, measurements of sun exposures by means other than questionnaires have been limited (5,6). New technologies have now devised easy to use personal ultraviolet dosimeters that are able to record exposure to ultraviolet A and ultraviolet B. These dosimeters could be used to investigate the characteristics of sun exposures known to be more strongly associated with melanoma occurrence (e.g., sunbathing).
As Gasparro and Berwick rightly indicate, we possess the tools to perform such research. Now we just need to mobilize the necessary resources to perform the research.
REFERENCES
1
Autier P, Dore JF, Cattaruza MS, Renard F, Luther H,
Gentiloni-Silveij F, 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.
2 International Agency for Research on Cancer. Solar and ultraviolet radiation. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol 55. Lyon (France): IARC; 1992. p. 139-61.
3 Elwood M, Jopson J. Melanoma and sun exposure: an overview of published studies. Int J Cancer 1997;73:198-203.[CrossRef][Web of Science][Medline]cancerlit;97474418
4
Marks R, Whiteman D. Sunburn and melanoma: how strong is
the evidence? BMJ 1994;308:75-6.
5 Diffey BL, Gibson CJ, Haylock R, McKinlay AF. Outdoor ultraviolet exposure of children and adolescents. Br J Dermatol 1996;134:1030-4.[Medline]
6 Dwyer T, Blizzard L, Gies PH, Ashbolt R, Roy C. Assessment of habitual sun exposure in adolescents via questionnaire—a comparison with objective measurement using polysulphone badges. Melanoma Res 1996;6:231-9.[CrossRef][Web of Science][Medline]
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