title: The impact of contralateral breast cancer on the outcome of breast cancer patients treated by mastectomy.
abstract: OBJECTIVE
  To evaluate the clinical and pathological features of breast cancer patients who develop contralateral breast cancer (CBC) and assess the impact of the second breast cancer on their prognosis.
  
  
  METHODS
  This retrospective study includes 2136 women with stage I-III breast cancer treated between 1927 and 1987 at the University of Chicago Hospitals. A total of 132 (6.2%) developed CBC during a median follow-up period of 14.2 years; all of them were treated with mastectomy for both breast cancers. We compare the prognostic characteristics, treatments, and outcomes of patients who developed bilateral breast cancer with those who had only unilateral breast cancer (UBC). We also compare the features of the first and the second tumors among patients with bilateral breast cancer (BBC).
  
  
  RESULTS
  The annual incidence rate for CBC remained constant at an average rate of 0.23%, resulting in a cumulative incidence rate of 6.2%. Patients with BBC were significantly younger than those with UBC (median age, 51 years vs 54 years). No other significant differences were observed between BBC and UBC patients. Among BBC patients, the second cancer was smaller (2.0 cm vs 3.0 cm) and was associated with a lower incidence of axillary node involvement (29% vs 52%). The development of CBC was associated with worse survival (hazard ratio = 1.46 in comparison with patients who did not develop CBC, 95% CI of 1.09-1.95). On multivariate analysis, factors that decreased the disease-specific survival (DSS) in patients with BBC were a higher number of positive lymph nodes of the first and second cancers, a larger size of the second cancer, and a shorter interval between the two primaries.
  
  
  CONCLUSIONS
  At the time of diagnosis of first breast cancer, BBC patients were significantly younger than UBC patients. The second cancer among the BBC patients was at an earlier stage than the first one; however, no difference was noticed in the pathological feature between the cancer in the UBC patients and the first cancer of BBC patients. There is an indication that the longer the interval between the two cancers, the better the survival of the BBC patients.
authors.affiliation: Department of Radiation and Cellular Oncology, The Pritzker School of Medicine, The University of Chicago Hospitals, Illinois, USA.
authors.forename: I
authors.initials: I
authors.lastname: Abdalla
authors.forename: R A
authors.initials: RA
authors.lastname: Thisted
authors.forename: R
authors.initials: R
authors.lastname: Heimann
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008408:Mastectomy; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000453:epidemiology / Q000473:pathology; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors