title: Topoisomerase II alpha gene amplification is a favorable prognostic factor in patients with HER2-positive metastatic breast cancer treated with trastuzumab.
abstract: BACKGROUND
  The vast majority of patients with HER2-positive metastatic breast cancer (MBC) treated with trastuzumab eventually develop resistance to this agent. There is an unmet need therefore, for identifying biological markers with possible prognostic/predictive value in such patients. The aim of this study was to investigate the prognostic role of topoisomerase II alpha gene (TOP2A) amplification and protein (TopoIIa) expression in patients treated with trastuzumab-containing regimens.
  
  
  METHODS
  Formalin-fixed paraffin-embedded tumor tissue samples were retrospectively collected from 225 eligible patients treated with trastuzumab. Protein expression of ER, PgR, Ki67, PTEN, HER2 and TopoIIa were centrally assessed by immunohistochemistry. HER2 and TOP2A gene amplification was evaluated by fluorescence in situ hybridization. PIK3CA mutations were identified by single nucleotide polymorphism genotyping. Survival was evaluated from the initiation of trastuzumab as 1st line treatment to the date of last follow-up or death.
  
  
  RESULTS
  Among the 225 samples analyzed, only 137 (61%) were found to be HER2-positive. TOP2A was amplified in 41% and deleted in 16% of such tumors. TOP2A gene amplification was more frequent in ER-negative tumors. TopoIIa protein expression was observed in the majority (65%) of the samples and was associated with ER-positive status, high Ki67 expression, presence of PTEN protein and PIK3CA mutations. Median follow-up for patients treated in the 1st line was 51 months. Survival was more prolonged with trastuzumab-containing treatment in HER2-positive patients (50 months, log-rank, p=0.007). TOP2A non-amplified or deleted tumors were associated with increased risk for death compared to TOP2A amplified tumors (HR=2.16, Wald's p=0.010 and HR=2.67, p=0.009, respectively). In multivariate analysis, a significant interaction of TOP2A with anthracycline treatment (either in the adjuvant or the 1st line setting) was observed for survival (Wald's p=0.015). Among the TOP2A amplified subgroup, anthracycline-treated patients were associated with decreased risk for death.
  
  
  CONCLUSIONS
  TOP2A gene amplification was shown to be a favorable prognostic marker in HER2-positive MBC patients treated with trastuzumab, such an effect however, appears to rather be related to treatment with anthracyclines (predictive marker for benefit from anthracyclines). The results of the present retrospective study warrant validation in larger cohorts of patients treated in the context of randomized trials.
authors.affiliation: Department of Medical Oncology, Papageorgiou Hospital, Aristotle University of Thessaloniki School of Medicine, 564 03, Thessaloniki, Macedonia, Greece. fountzil@auth.gr
authors.forename: George
authors.initials: G
authors.lastname: Fountzilas
authors.forename: Christos
authors.initials: C
authors.lastname: Christodoulou
authors.forename: Mattheos
authors.initials: M
authors.lastname: Bobos
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Kotoula
authors.forename: Anastasia G
authors.initials: AG
authors.lastname: Eleftheraki
authors.forename: Ioannis
authors.initials: I
authors.lastname: Xanthakis
authors.forename: Anna
authors.initials: A
authors.lastname: Batistatou
authors.forename: George
authors.initials: G
authors.lastname: Pentheroudakis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Xiros
authors.forename: Irene
authors.initials: I
authors.lastname: Papaspirou
authors.forename: Anna
authors.initials: A
authors.lastname: Koumarianou
authors.forename: Pavlos
authors.initials: P
authors.lastname: Papakostas
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Bafaloukos
authors.forename: Dimosthenis V
authors.initials: DV
authors.lastname: Skarlos
authors.forename: Konstantine T
authors.initials: KT
authors.lastname: Kalogeras
mesh_terms: D000951:Antigens, Neoplasm / Q000235:genetics*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D005260:Female; D018734:Genes, erbB-2; D006801:Humans; D007150:Immunohistochemistry; D009362:Neoplasm Metastasis; D016612:Paraffin Embedding; D000075223:Poly-ADP-Ribose Binding Proteins; D011379:Prognosis
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D004250:DNA Topoisomerases, Type II; C000618811:TOP2A protein, human