title: The risk of a contralateral breast cancer among women diagnosed with ductal and lobular breast carcinoma in situ: data from the Connecticut Tumor Registry.
abstract: BACKGROUND
  Women diagnosed with breast carcinoma in situ are at increased risk for developing a contralateral breast cancer. The magnitude of this risk and the relationship between this risk and age, time since diagnosis, histologic subtype, and treatment for the first breast cancer is continuing to be defined.
  
  
  METHODS
  The risk of developing a contralateral breast cancer is examined among 4198 women diagnosed with breast carcinoma in situ and reported to the Connecticut Tumor Registry (CTR) between January 1, 1975 and March 14, 1998 using Kaplan-Meier estimation. A Cox proportional hazards model is used to assess the effect of surgical treatment, radiation therapy, age at diagnosis, race, histology, marital status, anatomic location within the breast, and time since diagnosis upon this risk.
  
  
  RESULTS
  The cumulative 5- and 10-year probabilities of being diagnosed with a contralateral breast cancer among women initially diagnosed with a ductal breast carcinoma in situ (DCIS) were 4.3% (95% confidence interval, 3.6-5.0%) and 6.8% (95% confidence interval, 5.5-8.2%), respectively. These risks are 3.35 times greater than those for women without a history of breast cancer but are similar to those for women diagnosed with non-metastatic invasive ductal carcinomas of the breast. The cumulative 5- and 10-year probabilities of being diagnosed with a contralateral breast cancer among women initially diagnosed with a lobular breast carcinoma in situ (LCIS) were 11.9% (95% confidence interval, 9.5-14.3%) and 13.9% (95% confidence interval, 11.0-16.8%), respectively.
  
  
  CONCLUSIONS
  Women diagnosed with LCIS were 2.6 (95% confidence interval, 2.0-3.4%) times more likely than women with DCIS to be diagnosed with a contralateral breast cancer within the first six months of the first breast primary. The risk of developing a contralateral breast cancer more than 6 months after the initial breast cancer was independent of surgical or radiation therapy, time since diagnosis, age at diagnosis, histology, race, marital status, or anatomic location of the cancer within the breast.
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06510, USA. elizabeth.claus@yale.edu
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Claus
authors.forename: Meredith
authors.initials: M
authors.lastname: Stowe
authors.forename: Darryl
authors.initials: D
authors.lastname: Carter
authors.forename: Theodore
authors.initials: T
authors.lastname: Holford
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000453:epidemiology*; D018275:Carcinoma, Lobular / Q000453:epidemiology*; D003237:Connecticut; D005260:Female; D006801:Humans; D008875:Middle Aged; D016609:Neoplasms, Second Primary / Q000453:epidemiology*; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors