title: Tumor stage affects risk and prognosis of contralateral breast cancer: results from a large Swedish-population-based study.
abstract: OBJECTIVE
  The number of breast cancer survivors at risk of developing contralateral breast cancer (CBC) is increasing. However, ambiguity remains regarding risk factors and prognosis for women with CBC.
  
  
  METHODS
  In a cohort of 42,670 women with breast cancer in the Uppsala/Örebro and Stockholm regions in Sweden in 1992 to 2008, we assessed risk factors for and prognosis of metachronous CBC by using survival analysis. Breast cancer-specific survival for women with CBC was evaluated and compared with results for women with unilateral breast cancer (UBC) by using time-dependent Cox-regression modeling.
  
  
  RESULTS
  An increased risk for CBC was observed among women who had primary breast cancer with ≥ 10 involved lymph nodes compared with node-negative women (adjusted hazard ratio [HR], 1.8; 95% CI, 1.2 to 2.7). The prognosis was poorer in women with CBC than with UBC. The hazard of dying from breast cancer was especially high for women with a short interval time to CBC (adjusted HR, 2.3; 95% CI, 1.8 to 2.8 for CBC diagnosed ≤ 5 years v UBC) and gradually decreased with longer follow-up time but remained higher than the hazard originating from the primary tumor for ≥ 10 years.
  
  
  CONCLUSIONS
  Women with advanced-stage primary breast cancer had an increased risk of developing CBC. CBC is associated with an increased risk of dying from breast cancer throughout a long period of follow-up after the primary tumor. Our findings suggest that the event of CBC marks a new clinical situation in terms of investigations for metastases, treatment considerations, and follow-up strategy.
authors.affiliation: Division of Cancer Studies, King’s College London, London, United Kingdom.voralak.vichapat@kcl.ac.uk
authors.forename: Voralak
authors.initials: V
authors.lastname: Vichapat
authors.forename: Hans
authors.initials: H
authors.lastname: Garmo
authors.forename: Marit
authors.initials: M
authors.lastname: Holmqvist
authors.forename: Göran
authors.initials: G
authors.lastname: Liljegren
authors.forename: Fredrik
authors.initials: F
authors.lastname: Wärnberg
authors.forename: Mats
authors.initials: M
authors.lastname: Lambe
authors.forename: Tommy
authors.initials: T
authors.lastname: Fornander
authors.forename: Jan
authors.initials: J
authors.lastname: Adolfsson
authors.forename: Margreet
authors.initials: M
authors.lastname: Lüchtenborg
authors.forename: Lars
authors.initials: L
authors.lastname: Holmberg
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000401:mortality / Q000473:pathology*; D011379:Prognosis; D012307:Risk Factors; D015996:Survival Rate