title: Heterogeneity of metabolic response to systemic therapy in metastatic breast cancer patients.
abstract: OBJECTIVE
  The aim of this retrospective study was to describe the intra-individual heterogeneity of the ¹⁸F-labelled fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) response among lesions in bone-dominant metastatic breast cancer patients treated with systemic therapies.
  
  
  METHODS
  The metabolic response was analysed by comparing PET/CT scans carried out before and during a new treatment phase (n=46) in 25 bone-dominant metastatic breast cancer patients. Patients presented both bone and extra-bone metastases in 48% treatment phases. The metabolic response was analysed according to European Organization for Research and Treatment of Cancer (EORTC) criteria. A heterogeneous response was defined as the coexistence of responding and non-responding lesions within the same patient.
  
  
  RESULTS
  The lesion-based response analysis showed a heterogeneous metabolic response in 48% of treatment phases. In the subset with both bone and extra-bone metastases (n=20), PET/CT showed discordant responses between bone and extra-bone metastases in 6/20 (30%) treatment phases. Considering all the cases included in the study, the time to progression (TTP) was longer in cases with a metabolic response compared with the cases with a metabolic non-response (P=0.02). In cases with a PET/CT non-response, TTP seemed to be lower in those with a homogeneous non-response compared with those with a heterogeneous metabolic response (P=0.07).
  
  
  CONCLUSIONS
  Whole-body FDG-PET allows frequent heterogeneous responses after systemic therapy to be identified in bone-dominant metastatic breast cancer patients.
authors.affiliation: Department of Nuclear Medicine, Institut Jules Bordet, Brussels, Belgium. vhuyge@ulb.ac.be
authors.forename: V
authors.initials: V
authors.lastname: Huyge
authors.forename: C
authors.initials: C
authors.lastname: Garcia
authors.forename: J
authors.initials: J
authors.lastname: Alexiou
authors.forename: L
authors.initials: L
authors.lastname: Ameye
authors.forename: B
authors.initials: B
authors.lastname: Vanderlinden
authors.forename: M
authors.initials: M
authors.lastname: Lemort
authors.forename: P
authors.initials: P
authors.lastname: Bergmann
authors.forename: A
authors.initials: A
authors.lastname: Awada
authors.forename: J-J
authors.initials: JJ
authors.lastname: Body
authors.forename: P
authors.initials: P
authors.lastname: Flamen
mesh_terms: D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000556:secondary; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D018572:Disease-Free Survival; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D019788:Fluorodeoxyglucose F18