Objective:The aim of this study was to assess the differences in clinical appearance and prognosis of osteosarcoma between preadolescent and adolescent in Chinese patients and investigate whether age at diagnosis is a prognostic indicator.Methods:Between May 2002 and May 2009,ninety-six children with high-grade osteosarcoma treated at our institute were stratified according to the age of 10.There were 19 preadolescents(≤ 10 years) and 77 adolescents(10 years < age ≤ 19 years),and their medical records were reviewed and compared using Fisher exact tests.Overall survival and disease-free survival was estimated by Kaplan-Meier methods and compared using log-rank tests.The prognostic significance of the various factors on survival was examined by Cox regression analysis.Results:There were no significant differences in terms of Karnofsky Performance Status(KPS) score,Enneking stage,tumor location,histologic type,pathologic fracture,tumor necrosis rate,tumor size,relapse and frequencies of adjuvant chemotherapy between the two groups.A high proportion of preadolescent patients was treated with amputation(78.9% vs.44.2%;P = 0.01).The 5-year survival of the preadolescent and adolescent groups was(38 ± 14)% and(33 ± 10)%,and the 2-year disease free survival for each group was(45 ± 12)% and(44.4 ± 6.3)%,respectively.Our study showed that age did not have any statistical significance for survival(P = 0.803).Univariate analysis indicated that KPS score;frequencies of adjuvant chemotherapy,tumor size and relapse were significantly related to overall survival.Multivariate Cox regression analysis revealed that both frequencies of adjuvant chemotherapy and relapse were independently prognostic factors for survival.Conclusion:Clinical characteristics and survival between the preadolescents and adolescents with osteosarcoma in China were compatible.So we suggested that there did not need to treat preadolescents patients by alternative and/or aggressive therapies compared with adolescent patients. Objective: The aim of this study was to assess the differences in clinical appearance and prognosis of osteosarcoma between preadolescent and adolescent in Chinese patients and investigate whether age at diagnosis is a prognostic indicator. Methods: Between May 2002 and May 2009, ninety-six children with high-grade osteosarcoma treated at our institute were stratified according to the age of 10.There were 19 preadolescents (≤ 10 years) and 77 adolescents (10 years