title: Osteosarcoma of the flat bone.
abstract: OBJECTIVE
  We aimed to understand the biology of osteosarcoma of the flat bone, which is a rare tumor entity.
  
  
  METHODS
  Cases with osteosarcoma of the flat bone were compared with those of the extremity in order to evaluate their clinicopathologic characteristics. And the influences of heterogeneous treatment modalities on outcome were analyzed.
  
  
  RESULTS
  Tumors of the flat bone comprised 91 (11.3%) of 806 osteosarcoma cases. Eight cases were secondary osteosarcoma associated with previous radiotherapy. Patients with a flat bone tumor were significantly older and more likely to present with metastases at diagnosis than extremity tumor. The proportions of female sex and chondroblastic subtype were higher among flat bone tumors than among extremity tumors. The 5-year overall survival and event-free survival rates were 35.2 +/- 5.4% and 24.7 +/- 5.5%, respectively. Although age and histologic response to pre-operative chemotherapy were not related to outcome of flat bone tumors, treatment modality influenced the survival. Patients treated surgically had better outcomes than those treated by another means. Radiation therapy did not appear to be an effective local control measure as surgery.
  
  
  CONCLUSIONS
  Treatment outcome of the tumor of the flat bone was worse than extremity tumors. Further studies are needed to identify effective local control measures that can substitute for surgery and to determine the biologic characteristics of osteosarcoma of the flat bone.
authors.affiliation: Department of Orthopedic Surgery, Korea Cancer Center Hospital, 215-4 Gongneung-Dong, Nowon-Gu, 139-706 Seoul, Republic of Korea.
authors.forename: Jun Ah
authors.initials: JA
authors.lastname: Lee
authors.forename: Min Suk
authors.initials: MS
authors.lastname: Kim
authors.forename: Jae-Soo
authors.initials: JS
authors.lastname: Koh
authors.forename: Mi Sook
authors.initials: MS
authors.lastname: Kim
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Kim
authors.forename: Jung Sub
authors.initials: JS
authors.lastname: Lim
authors.forename: Chang-Bae
authors.initials: CB
authors.lastname: Kong
authors.forename: Won Seok
authors.initials: WS
authors.lastname: Song
authors.forename: Wan Hyeong
authors.initials: WH
authors.lastname: Cho
authors.forename: Soo-Yong
authors.initials: SY
authors.lastname: Lee
authors.forename: Dae-Geun
authors.initials: DG
authors.lastname: Jeon
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000453:epidemiology / Q000401:mortality / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery*; D002648:Child; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D012516:Osteosarcoma / Q000453:epidemiology / Q000401:mortality / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery*; D012189:Retrospective Studies; D055815:Young Adult