title: The relationship between quantitative human epidermal growth factor receptor 2 gene expression by the 21-gene reverse transcriptase polymerase chain reaction assay and adjuvant trastuzumab benefit in Alliance N9831.
abstract: BACKGROUND
  The N9831 trial demonstrated the efficacy of adjuvant trastuzumab for patients with human epidermal growth factor receptor 2 (HER2) locally positive tumors by protein or gene analysis. We used the 21-gene assay to examine the association of quantitative HER2 messenger RNA (mRNA) gene expression and benefit from trastuzumab.
  
  
  METHODS
  N9831 tested the addition of trastuzumab to chemotherapy in stage I-III HER2-positive breast cancer. For two of the arms of the trial, doxorubicin and cyclophosphamide followed by paclitaxel (AC-T) and doxorubicin and cyclophosphamide followed by paclitaxel and trastuzumab concurrent chemotherapy-trastuzumab (AC-TH), recurrence score (RS) and HER2 mRNA expression were determined by the 21-gene assay (Oncotype DX®) (negative <10.7, equivocal 10.7 to <11.5, and positive ≥11.5 log2 expression units). Cox regression was used to assess the association of HER2 expression with trastuzumab benefit in preventing distant recurrence.
  
  
  RESULTS
  Median follow-up was 7.4 years. Of 1,940 total patients, 901 had consent and sufficient tissue. HER2 by reverse transcriptase polymerase chain reaction (RT-PCR) was negative in 130 (14 %), equivocal in 85 (9 %), and positive in 686 (76 %) patients. Concordance between HER2 assessments was 95 % for RT-PCR versus central immunohistochemistry (IHC) (>10 % positive cells = positive), 91 % for RT-PCR versus central fluorescence in situ hybridization (FISH) (≥2.0 = positive) and 94 % for central IHC versus central FISH. In the primary analysis, the association of HER2 expression by 21-gene assay with trastuzumab benefit was marginally nonsignificant (nonlinear p = 0.057). In hormone receptor-positive patients (local IHC) the association was significant (p = 0.002). The association was nonlinear with the greatest estimated benefit at lower and higher HER2 expression levels.
  
  
  CONCLUSIONS
  Concordance among HER2 assessments by central IHC, FISH, and RT-PCR were similar and high. Association of HER2 mRNA expression with trastuzumab benefit as measured by time to distant recurrence was nonsignificant. A consistent benefit of trastuzumab irrespective of mHER2 levels was observed in patients with either IHC-positive or FISH-positive tumors. Trend for benefit was observed also for the small groups of patients with negative results by any or all of the central assays.
  
  
  BACKGROUND
  Clinicaltrials.gov NCT00005970 . Registered 5 July 2000.
authors.affiliation: Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL, 32224, USA. perez.edith@mayo.edu.
authors.forename: Edith A
authors.initials: EA
authors.lastname: Perez
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. RBaehner@genomichealth.com.|Department of Health Sciences Research, University of California, 500 Parnassus Avenue, San Francisco, CA, 94143, USA. RBaehner@genomichealth.com.
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Baehner
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. smbutler@genomichealth.com.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Butler
authors.affiliation: Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL, 32224, USA. thompson.aubrey@mayo.edu.
authors.forename: E Aubrey
authors.initials: EA
authors.lastname: Thompson
authors.affiliation: Alliance Statistics and Data Center, Mayo Clinic, 13400 E. Shea Boulevard, Scottsdale, AZ, USA. Dueck.Amylou@mayo.edu.
authors.forename: Amylou C
authors.initials: AC
authors.lastname: Dueck
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. FJamshidian@genomichealth.com.
authors.forename: Farid
authors.initials: F
authors.lastname: Jamshidian
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. DCherbavaz@genomichealth.com.
authors.forename: Diana
authors.initials: D
authors.lastname: Cherbavaz
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. CYoshizawa@genomichealth.com.
authors.forename: Carl
authors.initials: C
authors.lastname: Yoshizawa
authors.affiliation: Genomic Health, Inc, 301 Penobscot Drive, Redwood City, CA, 94063, USA. sshak@genomichealth.com.
authors.forename: Steven
authors.initials: S
authors.lastname: Shak
authors.affiliation: Norris Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH, 03766, USA. Peter.A.Kaufman@hitchcock.org.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Kaufman
authors.affiliation: University of Pittsburgh Cancer Institute, 5150 Centre Avenue, Pittsburgh, PA, 15232, USA. davidsonne@upmc.edu.
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Davidson
authors.affiliation: Seattle Cancer Care Alliance, 825 Eastlake Avenue East, Seattle, WA, 98109, USA. pink@u.washington.edu.
authors.forename: Julie
authors.initials: J
authors.lastname: Gralow
authors.affiliation: Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL, 32224, USA. Asmann.Yan@mayo.edu.
authors.forename: Yan W
authors.initials: YW
authors.lastname: Asmann
authors.affiliation: Alliance Statistics and Data Center, 200 1st Street SW, Mayo Clinic, Rochester, MN, 55905, USA. Ballman.Karla@mayo.edu.
authors.forename: Karla V
authors.initials: KV
authors.lastname: Ballman
mesh_terms: D000293:Adolescent; D000328:Adult; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D018572:Disease-Free Survival; D019008:Drug Resistance, Neoplasm; D005260:Female; D015870:Gene Expression; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000378:metabolism* / Q000401:mortality / Q000517:prevention & control; D016016:Proportional Hazards Models; D016032:Randomized Controlled Trials as Topic; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000068878:Trastuzumab / Q000494:pharmacology* / Q000627:therapeutic use; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C508053:ERBB2 protein, human