title: Association between contralateral prophylactic mastectomy and breast cancer outcomes by hormone receptor status.
abstract: BACKGROUND
  The effect of contralateral prophylactic mastectomy (CPM) on the survival of patients with early-stage breast cancer remains controversial. The objective of this study was to evaluate the benefits of CPM using a propensity scoring approach that reduces selection bias from the nonrandom assignment of patients in observational studies.
  
  
  METHODS
  A total of 3889 female patients with stage I to III breast cancer were identified who were treated at The University of Texas MD Anderson Cancer Center from 1997 to 2009. We assessed the association between CPM and disease-free (DFS) and overall survival (OS), by using Cox proportional hazards models to estimate hazard ratios (HRs), and by matching patients in the CPM and no-CPM groups using propensity scores (n = 497 pairs).
  
  
  RESULTS
  With a median follow-up time of 4.5 years, CPM was associated with improved DFS (HR, 0.75; 95% confidence interval [CI], 0.59-0.97) and OS (HR, 0.74; 95% CI, 0.56-0.99), adjusted for prognostic factors. The improved DFS was seen predominantly among hormone receptor-negative (HR, 0.60; 95% CI, 0.38-0.95) compared with hormone receptor-positive patients (HR, 0.80; 95% CI, 0.58-1.10). For the matched patient cohort, stratified survival analysis also showed an improvement in DFS with CPM (HR, 0.48; 95% CI, 0.22-1.01) in hormone receptor-negative patients that was nearly statistically significant.
  
  
  CONCLUSIONS
  CPM was associated with improved DFS for some patients with hormone receptor-negative breast cancer, after reducing selection bias. Identifying subsets of patients most likely to benefit from CPM may have important implications for a more personalized approach to treatment decisions about CPM.
authors.affiliation: Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, Texas 77230-1439, USA. abrewster@mdanderson.org
authors.forename: Abenaa M
authors.initials: AM
authors.lastname: Brewster
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bedrosian
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Parker
authors.forename: Wenli
authors.initials: W
authors.lastname: Dong
authors.forename: Susan K
authors.initials: SK
authors.lastname: Peterson
authors.forename: Scott B
authors.initials: SB
authors.lastname: Cantor
authors.forename: Melissa
authors.initials: M
authors.lastname: Crosby
authors.forename: Yu
authors.initials: Y
authors.lastname: Shen
mesh_terms: D001940:Breast / Q000601:surgery; D001943:Breast Neoplasms / Q000378:metabolism / Q000401:mortality / Q000601:surgery*; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008408:Mastectomy; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D016896:Treatment Outcome
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human