Abstract: Objective To analyze the factors affecting the therapeutic effect of Q-switched alexandrite laser on and recurrence of café-au-lait spots. Methods A follow up was conducted in patients with café-au-lait spots treated with Q-switched alexandrite laser in the Nineth People′s Hospital, Shanghai Jiao Tong University School of Medicine from January of 2002 to December of 2006. Groups were classified according to the age, gender, onset age, disease course, treatment interval of patients as well as the number, area, site, shape, color depth, etc, of lesions. Chi-Square test was used to compare the difference in response rate and recurrence rate among different groups. Results A total of 351 valid cases were collected, among which 73 were males, 278 were females, with a total recurrence rate of 84.6% and total response rate of 53.3%. Neither response rate nor recurrence rate significantly correlated with the gender, treatment age or disease course of patients （all P > 0.05）. However, the therapeutic effect was significantly affected by the age of onset （χ2 = 6.162, P < 0.05）, lesional site （χ2 = 14.196, P < 0.001）, area（χ2 = 13.005, P < 0.05）, color depth（χ2 = 10.063, P < 0.05）, shape （χ2 = 14.039, P < 0.001）and treatment interval （χ2 = 4.787, P < 0.05）. More treatment sessions were associated with a higher efficacy （r = 0.343, P < 0.001）, and higher treatment energy within a certain range were associated with a better therapeutic effect （r = 0.178, P < 0.01） and longer treatment interval （r = 0.157, P < 0.05）. Conclusions Q-switched alexandrite laser is an effective approach to the treatment of café-au-lait spots, and its efficacy can be predicted according to different factors that concern.

Key words: Treatment outcome