Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Sunscreens, Nevi, and Melanoma Revisited

Sunscreens, Nevi, and Melanoma Revisited Broad-spectrum sunscreen use and the development of new nevi in white children: a randomized controlled trial.Richard P. Gallagher; Jason K. Rivers; Tim K. Lee; Chris D. Bajdik; David I. McLean; Andrew J. ColdmanJAMA. 2000;283:2955-2960 The relationship between sunscreen use and the risk of melanoma is controversial. Previous case-control studies have shown rates of sunscreen use in patients with melanoma that were higher than, the same as, or lower than in those in controls.1 Because high nevi counts are a predictor of melanoma, the objective of this prospective, randomized controlled study was to determine whether the use of a "broad-spectrum" sunscreen with a sun protection factor of 30 attenuates the development of melanocytic nevi in white Canadian children. A total of 458 schoolchildren in British Columbia in grades 1 and 4 were randomized in 1993. Parents of the 222 children assigned to the treatment group received a supply of sunscreen with directions to apply it to exposed sites when the child was expected to be in the sun for 30 minutes or more. Parents of the 236 children assigned to the control group received no sunscreen or placebo and were given no advice about sunscreen use. Each child's nevi were enumerated at the start of the study in 1993 and at the end of the study in 1996. After the exclusion of children with dark complexions and those lost to follow-up or with missing data, 309 white children remained for analysis. Comparisons between groups were based on median values, and differences were assessed using the Kruskal-Wallis test (a nonparametric test for the significance of the difference among the distributions of ≥3 independent samples).2,3 Children in the sunscreen group developed fewer nevi than children in the control group (median count, 24 vs 28; P = .048). Estimates generated using a linear regression model controlling for grade in school, sex, and hair color indicated that being heavily freckled and being randomized to the sunscreen group together constituted the statistically strongest negative predictor for developing new nevi (ie, heavily freckled children randomized to the sunscreen group developed fewer nevi than heavily freckled children in the control group). Linear regression models are used to analyze the relationship between 2 variables, which in this case was the relationship between the number of new nevi and the percentage of the face covered by freckles.2,3 Children with no freckling had little advantage when randomized to the sunscreen group compared with the control group. The authors conclude that broad-spectrum sunscreens may attenuate the number of nevi in white children, especially if they have freckles. Editor's Comment The strengths of this study are that (1) it was prospective, (2) there was concealed randomization of children, (3) it was observer-masked, (4) there was objective assessment of outcome, and (5) there was careful adjustment for confounding factors in the analysis of the data. The weaknesses of the study are the lack of subject masking, unequal treatment of groups, and the inclusion of only patients who completed the study in the analysis.4 The study represents an unprecedented addition to the available evidence about the relationship between the use of sunscreens and development of nevi in childhood. It provides evidence that, at least for white, freckled children, the use of a broad-spectrum sunscreen with a high sun protection factor attenuates the development of nevi and, by deduction, decreases the risk of developing a melanoma. The results of this and previous case-control studies raise the very serious question of what to do when there is conflicting evidence. With regard to the use of sunscreen and the risk of melanoma, several options are available. One could conclude that, since this prospective, randomized, controlled, observer-masked study has the strongest design (which is most likely to minimize the influence of bias or chance), the use of sunscreens decreases the risk of melanoma and that previous studies indicating the opposite conclusion are biased and can be dismissed. One could attempt to do a systematic review and meta-analysis of available data and potentially reach a conclusion. One could take a simplistic approach and add up the number of studies favoring either side of the issue and go with the side with the most studies. One could conclude that both hypotheses are correct and that the use of a broad-spectrum sunscreen with a high sun protection factor decreases the risk of developing a melanoma and that misuse of sunscreen or use of inadequate sunscreen increases the risk of developing a melanoma. Finally, one could conclude that since there is conflicting evidence, one cannot draw any firm conclusions. As practicing dermatologists in a world in which evidence is often imperfect, the best available evidence would suggest counseling patients to lower their exposure to sunlight and advising them that the use of a broad-spectrum sunscreen with a high protection factor decreases the risk of developing melanoma, especially in children with freckles. A cooperative effort of the Clinical Epidemiology Unit of the Istituto Dermopatico dell'Immacolata–Istituto di Recovero e Cura a Carattere Scientifico (IDI-IRCCS) and the Archives of Dermatology References 1. Bigby M The sunscreen and melanoma controversy. Arch Dermatol. 1999;1351526- 1527Google Scholar 2. Glantz SA Primer of Biostatistics. 4th ed. New York, NY McGraw-Hill Co1997;218- 277 3. Not Available, InStat guide to choosing and interpreting statistical tests. Available athttp://www.graphpad.com/instatman/instat3.htmAccessibility verified October 10, 2000. 4. Guyatt GHSackett DLCook DJfor the Evidence-Based Medicine Working Group, Users' guides to the medical literature, II: how to use an article about therapy or prevention, A: are the results of the study valid? JAMA. 1993;2702598- 2601Google ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Dermatology American Medical Association

Sunscreens, Nevi, and Melanoma Revisited

Archives of Dermatology , Volume 136 (12) – Dec 1, 2000

Loading next page...
 
/lp/american-medical-association/sunscreens-nevi-and-melanoma-revisited-s0UCDclmha
Publisher
American Medical Association
Copyright
Copyright © 2000 American Medical Association. All Rights Reserved.
ISSN
0003-987X
eISSN
1538-3652
DOI
10.1001/archderm.136.12.1549
Publisher site
See Article on Publisher Site

Abstract

Broad-spectrum sunscreen use and the development of new nevi in white children: a randomized controlled trial.Richard P. Gallagher; Jason K. Rivers; Tim K. Lee; Chris D. Bajdik; David I. McLean; Andrew J. ColdmanJAMA. 2000;283:2955-2960 The relationship between sunscreen use and the risk of melanoma is controversial. Previous case-control studies have shown rates of sunscreen use in patients with melanoma that were higher than, the same as, or lower than in those in controls.1 Because high nevi counts are a predictor of melanoma, the objective of this prospective, randomized controlled study was to determine whether the use of a "broad-spectrum" sunscreen with a sun protection factor of 30 attenuates the development of melanocytic nevi in white Canadian children. A total of 458 schoolchildren in British Columbia in grades 1 and 4 were randomized in 1993. Parents of the 222 children assigned to the treatment group received a supply of sunscreen with directions to apply it to exposed sites when the child was expected to be in the sun for 30 minutes or more. Parents of the 236 children assigned to the control group received no sunscreen or placebo and were given no advice about sunscreen use. Each child's nevi were enumerated at the start of the study in 1993 and at the end of the study in 1996. After the exclusion of children with dark complexions and those lost to follow-up or with missing data, 309 white children remained for analysis. Comparisons between groups were based on median values, and differences were assessed using the Kruskal-Wallis test (a nonparametric test for the significance of the difference among the distributions of ≥3 independent samples).2,3 Children in the sunscreen group developed fewer nevi than children in the control group (median count, 24 vs 28; P = .048). Estimates generated using a linear regression model controlling for grade in school, sex, and hair color indicated that being heavily freckled and being randomized to the sunscreen group together constituted the statistically strongest negative predictor for developing new nevi (ie, heavily freckled children randomized to the sunscreen group developed fewer nevi than heavily freckled children in the control group). Linear regression models are used to analyze the relationship between 2 variables, which in this case was the relationship between the number of new nevi and the percentage of the face covered by freckles.2,3 Children with no freckling had little advantage when randomized to the sunscreen group compared with the control group. The authors conclude that broad-spectrum sunscreens may attenuate the number of nevi in white children, especially if they have freckles. Editor's Comment The strengths of this study are that (1) it was prospective, (2) there was concealed randomization of children, (3) it was observer-masked, (4) there was objective assessment of outcome, and (5) there was careful adjustment for confounding factors in the analysis of the data. The weaknesses of the study are the lack of subject masking, unequal treatment of groups, and the inclusion of only patients who completed the study in the analysis.4 The study represents an unprecedented addition to the available evidence about the relationship between the use of sunscreens and development of nevi in childhood. It provides evidence that, at least for white, freckled children, the use of a broad-spectrum sunscreen with a high sun protection factor attenuates the development of nevi and, by deduction, decreases the risk of developing a melanoma. The results of this and previous case-control studies raise the very serious question of what to do when there is conflicting evidence. With regard to the use of sunscreen and the risk of melanoma, several options are available. One could conclude that, since this prospective, randomized, controlled, observer-masked study has the strongest design (which is most likely to minimize the influence of bias or chance), the use of sunscreens decreases the risk of melanoma and that previous studies indicating the opposite conclusion are biased and can be dismissed. One could attempt to do a systematic review and meta-analysis of available data and potentially reach a conclusion. One could take a simplistic approach and add up the number of studies favoring either side of the issue and go with the side with the most studies. One could conclude that both hypotheses are correct and that the use of a broad-spectrum sunscreen with a high sun protection factor decreases the risk of developing a melanoma and that misuse of sunscreen or use of inadequate sunscreen increases the risk of developing a melanoma. Finally, one could conclude that since there is conflicting evidence, one cannot draw any firm conclusions. As practicing dermatologists in a world in which evidence is often imperfect, the best available evidence would suggest counseling patients to lower their exposure to sunlight and advising them that the use of a broad-spectrum sunscreen with a high protection factor decreases the risk of developing melanoma, especially in children with freckles. A cooperative effort of the Clinical Epidemiology Unit of the Istituto Dermopatico dell'Immacolata–Istituto di Recovero e Cura a Carattere Scientifico (IDI-IRCCS) and the Archives of Dermatology References 1. Bigby M The sunscreen and melanoma controversy. Arch Dermatol. 1999;1351526- 1527Google Scholar 2. Glantz SA Primer of Biostatistics. 4th ed. New York, NY McGraw-Hill Co1997;218- 277 3. Not Available, InStat guide to choosing and interpreting statistical tests. Available athttp://www.graphpad.com/instatman/instat3.htmAccessibility verified October 10, 2000. 4. Guyatt GHSackett DLCook DJfor the Evidence-Based Medicine Working Group, Users' guides to the medical literature, II: how to use an article about therapy or prevention, A: are the results of the study valid? JAMA. 1993;2702598- 2601Google ScholarCrossref

Journal

Archives of DermatologyAmerican Medical Association

Published: Dec 1, 2000

Keywords: melanoma,nevus,sunscreening agents

References