title: Validation of cytoplasmic-to-nuclear ratio of survivin as an indicator of improved prognosis in breast cancer.
abstract: BACKGROUND
  Conflicting data exist regarding the prognostic and predictive impact of survivin (BIRC5) in breast cancer. We previously reported survivin cytoplasmic-to-nuclear ratio (CNR) as an independent prognostic indicator in breast cancer. Here, we validate survivin CNR in a separate and extended cohort. Furthermore, we present new data suggesting that a low CNR may predict outcome in tamoxifen-treated patients.
  
  
  METHODS
  Survin expression was assessed using immunhistochemistry on a breast cancer tissue microarray (TMA) containing 512 tumours. Whole slide digital images were captured using an Aperio XT scanner. Automated image analysis was used to identify tumour from stroma and then to quantify tumour-specific nuclear and cytoplasmic survivin. A decision tree model selected using a 10-fold cross-validation approach was used to identify prognostic subgroups based on nuclear and cytoplasmic survivin expression.
  
  
  RESULTS
  Following optimisation of the staining procedure, it was possible to evaluate survivin protein expression in 70.1% (n = 359) of the 512 tumours represented on the TMA. Decision tree analysis predicted that nuclear, as opposed to cytoplasmic, survivin was the most important determinant of overall survival (OS) and breast cancer-specific survival (BCSS). The decision tree model confirmed CNR of 5 as the optimum threshold for survival analysis. Univariate analysis demonstrated an association between a high CNR (>5) and a prolonged BCSS (HR 0.49, 95% CI 0.29-0.81, p = 0.006). Multivariate analysis revealed a high CNR (>5) was an independent predictor of BCSS (HR 0.47, 95% CI 0.27-0.82, p = 0.008). An increased CNR was associated with ER positive (p = 0.045), low grade (p = 0.007), Ki-67 (p = 0.001) and Her2 (p = 0.026) negative tumours. Finally, a high CNR was an independent predictor of OS in tamoxifen-treated ER-positive patients (HR 0.44, 95% CI 0.23-0.87, p = 0.018).
  
  
  CONCLUSIONS
  Using the same threshold as our previous study, we have validated survivin CNR as a marker of good prognosis in breast cancer in a large independent cohort. These findings provide robust evidence of the importance of survivin CNR as a breast cancer biomarker, and its potential to predict outcome in tamoxifen-treated patients.
authors.affiliation: UCD Conway Institute, University College Dublin, Belfield, Ireland.
authors.forename: Elton
authors.initials: E
authors.lastname: Rexhepaj
authors.forename: Karin
authors.initials: K
authors.lastname: Jirstrom
authors.forename: Darran P
authors.initials: DP
authors.lastname: O'Connor
authors.forename: Sallyann L
authors.initials: SL
authors.lastname: O'Brien
authors.forename: Goran
authors.initials: G
authors.lastname: Landberg
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Duffy
authors.forename: Donal J
authors.initials: DJ
authors.lastname: Brennan
authors.forename: William M
authors.initials: WM
authors.lastname: Gallagher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000737:chemistry* / Q000401:mortality / Q000628:therapy; D002467:Cell Nucleus / Q000737:chemistry*; D016009:Chi-Square Distribution; D003593:Cytoplasm / Q000737:chemistry*; D003663:Decision Trees; D020847:Estrogen Receptor Modulators / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007150:Immunohistochemistry; D051034:Inhibitor of Apoptosis Proteins; D053208:Kaplan-Meier Estimate; D019394:Ki-67 Antigen / Q000032:analysis; D008869:Microtubule-Associated Proteins / Q000032:analysis*; D008875:Middle Aged; D010363:Pattern Recognition, Automated; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D000077022:Survivin; D013548:Sweden; D013629:Tamoxifen / Q000627:therapeutic use; D013997:Time Factors; D046888:Tissue Array Analysis; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D020847:Estrogen Receptor Modulators; D051034:Inhibitor of Apoptosis Proteins; D019394:Ki-67 Antigen; D008869:Microtubule-Associated Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D000077022:Survivin; D013629:Tamoxifen; C107489:BIRC5 protein, human; C508053:ERBB2 protein, human