title: 18F-FDG PET response to neoadjuvant chemotherapy for Ewing sarcoma and osteosarcoma are different.
abstract: OBJECTIVE
  Ewing sarcoma (ES) and osteosarcoma (OS) have different biological characteristics and respond differently to chemotherapy. We reviewed (18)F-FDG PET imaging characteristics of ES and OS patients at baseline and following treatment to determine whether this biological variation is reflected in their imaging phenotype.
  
  
  METHODS
  A retrospective review of ES and OS patients treated with neoadjuvant chemotherapy and surgery was done, correlating PET results with histologic response to chemotherapy.
  
  
  RESULTS
  Change in the maximum standardized uptake value (SUVmax) between baseline and post-treatment scanning was not significantly associated with histologic response for either ES or OS. Metabolic tumor volume (MTV) and the percentage of injected (18)F-FDG dose (%ID) in the primary tumor were found to be different for ES and OS response subgroups. A 50% reduction in MTV (MTV2:1 < 0.5) was found to be significantly associated with favorable histologic response in OS. Using the same criteria for ES incorrectly predicted good responders. Increasing the cut-off values for ES to a 90% reduction in MTV (MTV2:1 < 0.1) resulted in association with favorable histologic response.
  
  
  CONCLUSIONS
  Response to neoadjuvant chemotherapy as reflected by changes in PET characteristics should be interpreted differently for ES and OS.
authors.affiliation: Department of Orthopedics, Philippine General Hospital, Manila, Philippines. mutch95@yahoo.com
authors.forename: Louie L
authors.initials: LL
authors.lastname: Gaston
authors.forename: Claudia
authors.initials: C
authors.lastname: Di Bella
authors.forename: John
authors.initials: J
authors.lastname: Slavin
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Hicks
authors.forename: Peter F M
authors.initials: PF
authors.lastname: Choong
mesh_terms: D000293:Adolescent; D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D012516:Osteosarcoma / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012512:Sarcoma, Ewing / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18