title: Osteosarcoma in very young children: experience of the Cooperative Osteosarcoma Study Group.
abstract: BACKGROUND
  This study was conducted to investigate presentation, treatment, and outcome in very young children with osteosarcoma.
  
  
  METHODS
  The authors retrospectively analyzed the data of 2706 consecutive COSS patients with newly diagnosed osteosarcoma and identified 28 (1.0%) patients aged younger than 5 years at diagnosis. Demographic, diagnostic, tumor, treatment-related variables, response, and survival data were analyzed.
  
  
  RESULTS
  Of the 28 preschoolers, 27 presented with high-grade central osteosarcoma of an extremity, and 1 had a secondary osteosarcoma of the orbit. This analysis focused on the 27 patients with extremity tumors. The size of the primary was large (≥one-third of the involved bone) in 20 of 27 patients. Primary metastases were detected in 4 of 27 children. All patients received multiagent chemotherapy, and 11 of 18 analyzed tumors responded well (>90% necrosis) to neoadjuvant chemotherapy. Limb-sparing surgery was performed in 9 cases, ablative procedures were performed in 15, and, in 3 cases, no local surgery was performed. With a median follow-up of 4 years (6.2 years for survivors), 13 patients were alive. Four patients never achieved a complete remission, and 11 developed recurrences; 14 of these 15 patients died. Five-year overall and event-free survival probabilities were 51% (standard error of the mean [SE], 10%) and 48% (SE, 10%). Better survival was correlated with good response to chemotherapy and later time period of diagnosis.
  
  
  CONCLUSIONS
  Osteosarcoma is extremely rare in preschool children. These patients often have large tumors that may require mutilating resections. Prognosis is in the range of that reported for older patients.
authors.affiliation: St. Anna Children's Hospital, Vienna, Austria.
authors.forename: Leo
authors.initials: L
authors.lastname: Kager
authors.forename: Andreas
authors.initials: A
authors.lastname: Zoubek
authors.forename: Martin
authors.initials: M
authors.lastname: Dominkus
authors.forename: Susanna
authors.initials: S
authors.lastname: Lang
authors.forename: Nicole
authors.initials: N
authors.lastname: Bodmer
authors.forename: Gernot
authors.initials: G
authors.lastname: Jundt
authors.forename: Thomas
authors.initials: T
authors.lastname: Klingebiel
authors.forename: Heribert
authors.initials: H
authors.lastname: Jürgens
authors.forename: Helmut
authors.initials: H
authors.lastname: Gadner
authors.forename: Stefan
authors.initials: S
authors.lastname: Bielack
mesh_terms: D001132:Arm; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000473:pathology / Q000628:therapy*; D017024:Chemotherapy, Adjuvant; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D009362:Neoplasm Metastasis; D012516:Osteosarcoma / Q000175:diagnosis* / Q000401:mortality / Q000473:pathology / Q000628:therapy*; D016896:Treatment Outcome