title: Annual surveillance mammography after early-stage breast cancer and breast cancer mortality.
abstract: BACKGROUND
  After treatment for early-stage breast cancer (bca), annual surveillance mammography (asm) is recommended based on the assumption that early detection of an invasive ipsilateral breast tumour recurrence or subsequent invasive contralateral primary bca reduces bca mortality.
  
  
  METHODS
  We studied women with unilateral early-stage bca treated by breast-conserving surgery from 1994 to 1997 who subsequently developed an ipsilateral recurrence or contralateral primary more than 24 months after initial diagnosis, without prior regional or distant metastases. Annual surveillance mammography was defined as 2 episodes of bilateral mammography 11-18 months apart during the 2 years preceding the ipsilateral recurrence or contralateral primary. The association between asm and bca death was evaluated using a Cox proportional hazards model.
  
  
  RESULTS
  We identified 669 women who experienced invasive ipsilateral recurrence (n= 455) or a contralateral primary (n= 214) at a median interval of 53 months [interquartile range (iqr): 37-72 months] after initial diagnosis, 64.7% of whom had received asm during the preceding 2 years. The median interval between the 2 bilateral mammograms was 12.3 months (iqr: 11.9-13.0 months), and the median interval between the 2nd mammogram and histopathologic confirmation of ipsilateral recurrence or contralateral primary was 1.5 months (iqr: 0.8-3.9 months). Median followup after ipsilateral recurrence or contralateral primary was 7.76 years (iqr: 3.68-9.81 years). The adjusted hazard ratio for bca death associated with asm was 0.86 (95% confidence limits: 0.63, 1.16).
  
  
  CONCLUSIONS
  Annual surveillance mammography was associated with a modestly lowered hazard ratio for bca death.
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, ON.
authors.forename: L F
authors.initials: LF
authors.lastname: Paszat
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, ON.
authors.forename: R
authors.initials: R
authors.lastname: Sutradhar
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, ON.
authors.forename: S
authors.initials: S
authors.lastname: Gu
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, ON.
authors.forename: E
authors.initials: E
authors.lastname: Rakovitch
keywords: Breast cancer; contralateral breast cancer; local recurrence; mortality; propensity score adjustment; proportional hazards regression; surveillance mammography