The effect of a school-based sun protection intervention on the development of melanocytic nevi in children: 6-year follow-up.

Because nevi share risk factors with melanoma and are strong risk factors for melanoma, they are suitable biomarkers for evaluating sun protection programs. Kidskin was a trial of a school-based sun protection program in Western Australia that included high and moderate intervention groups and a control group. Schools were assigned nonrandomly to groups. The primary outcome was number of nevi on the back. Nevi were counted at baseline, after 4 years intervention and again 2 years later. Linear growth models, allowing for correlated data within schools and children were fitted to the data. The primary analysis included 639 control children, 414 in the moderate and 355 in the high intervention group. Compared with the control group, the relative increase in number of nevi on the back was 0.89 (95% confidence interval, 0.81-0.99) for the high intervention group and 0.94 (95% confidence interval, 0.86-1.04) for the moderate group (P = 0.09). In subgroup analyses of nevi on the back, the association was stronger in boys (P < 0.001) than in girls (P = 0.7), although the test for interaction was not significant (P = 0.11). For the chest, examined in boys, the associations were similar to that for nevi on the back in boys. Associations were weak for nevi on the face and arms (P = 0.2); for this site, there was weak evidence of heterogeneity by sex. Overall, there was weak evidence that the Kidskin intervention reduced the number of new nevi over a 6-year period, but there was stronger evidence of an effect on the trunk in boys.