title: Genomic index of sensitivity to endocrine therapy for breast cancer.
abstract: OBJECTIVE
  We hypothesize that measurement of gene expression related to estrogen receptor α (ER; gene name ESR1) within a breast cancer sample represents intrinsic tumoral sensitivity to adjuvant endocrine therapy.
  
  
  METHODS
  A genomic index for sensitivity to endocrine therapy (SET) index was defined from genes coexpressed with ESR1 in 437 microarray profiles from newly diagnosed breast cancer, unrelated to treatment or outcome. The association of SET index and ESR1 levels with distant relapse risk was evaluated from microarrays of ER-positive breast cancer in two cohorts who received 5 years of tamoxifen alone as adjuvant endocrine therapy (n = 225 and 298, respectively), a cohort who received neoadjuvant chemotherapy followed by tamoxifen and/or aromatase inhibition (n = 122), and two cohorts who received no adjuvant systemic therapy (n = 208 and 133, respectively).
  
  
  RESULTS
  The SET index (165 genes) was significantly associated with distant relapse or death risk in both tamoxifen-treated cohorts (hazard ratio [HR] = 0.70, 95% CI, 0.56 to 0.88, P = .002; and HR = 0.76, 95% CI, 0.63 to 0.93, P = .007) and in the chemo-endocrine-treated cohort (HR = 0.19; 95% CI, 0.05 to 0.69, P = .011) independently from pathologic response to chemotherapy, but was not prognostic in two untreated cohorts. No distant relapse or death was observed after tamoxifen alone if node-negative and high SET or after chemo-endocrine therapy if intermediate or high SET.
  
  
  CONCLUSIONS
  The SET index of ER-related transcription predicted survival benefit from adjuvant endocrine therapy, not inherent prognosis. Prior chemotherapy seemed to enhance the efficacy of adjuvant endocrine therapy related to SET index.
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA. fsymmans@mdanderson.org
authors.forename: W Fraser
authors.initials: WF
authors.lastname: Symmans
authors.forename: Christos
authors.initials: C
authors.lastname: Hatzis
authors.forename: Christos
authors.initials: C
authors.lastname: Sotiriou
authors.forename: Fabrice
authors.initials: F
authors.lastname: Andre
authors.forename: Florentia
authors.initials: F
authors.lastname: Peintinger
authors.forename: Peter
authors.initials: P
authors.lastname: Regitnig
authors.forename: Guenter
authors.initials: G
authors.lastname: Daxenbichler
authors.forename: Christine
authors.initials: C
authors.lastname: Desmedt
authors.forename: Julien
authors.initials: J
authors.lastname: Domont
authors.forename: Christian
authors.initials: C
authors.lastname: Marth
authors.forename: Suzette
authors.initials: S
authors.lastname: Delaloge
authors.forename: Thomas
authors.initials: T
authors.lastname: Bauernhofer
authors.forename: Vicente
authors.initials: V
authors.lastname: Valero
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Booser
authors.forename: Gabriel N
authors.initials: GN
authors.lastname: Hortobagyi
authors.forename: Lajos
authors.initials: L
authors.lastname: Pusztai
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000401:mortality / Q000556:secondary; D017024:Chemotherapy, Adjuvant; D016009:Chi-Square Distribution; D018572:Disease-Free Survival; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D023281:Genomics / Q000379:methods; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D020411:Oligonucleotide Array Sequence Analysis; D018579:Patient Selection; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D013629:Tamoxifen / Q000627:therapeutic use; D013997:Time Factors; D014158:Transcription, Genetic; D016896:Treatment Outcome
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D014408:Biomarkers, Tumor; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D013629:Tamoxifen