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Table 3 Cumulative incidence of contralateral breast cancer among 1-year survivors of a first primary breast cancer diagnosed in the recent treatment era between 2004 and 2015 (followed through to 2016) in 12 SEER registries

From: Risk of contralateral breast cancer according to first breast cancer characteristics among women in the USA, 1992–2016

First breast cancer characteristic 5-year cumulative incidence (95% CIs)a
Overall 1.31% (1.26 to 1.37%)
Age at diagnosis, years
 < 40 1.54% (1.27 to 1.85%)
 40 to < 50 1.15% (1.03 to 1.28%)
 50 to < 60 1.24% (1.13 to 1.35%)
 60 to < 70 1.33% (1.22 to 1.45%)
 ≥ 70 1.47% (1.35 to 1.60%)
Stage at diagnosis
 I 1.32% (1.24 to 1.40%)
 II 1.17% (1.08 to 1.26%)
 III 1.73% (1.55 to 1.93%)
ER status
 Positive 1.19% (1.13 to 1.26%)
 Negative 1.81% (1.66 to 1.98%)
ER status and age at diagnosis
 ER-positive
  < 50 years 1.01% (0.90 to 1.14%)
  ≥ 50 years 1.24% (1.17 to 1.32%)
 ER-negative
  < 50 years 1.89% (1.61 to 2.21%)
  ≥ 50 years 1.78% (1.60 to 1.97%)
HER2-statusb
 Positive 1.35% (1.05 to 1.71%)
 Negative 1.33% (1.21 to 1.45%)
Breast cancer subtypeb,c
 HR+/HER2+ 1.39% (1.02 to 1.84%)
 HR+/HER2− 1.27% (1.15 to 1.41%)
 HR−/HER2+ 1.27% (0.80 to 1.94%)
 HR-/HER2- (triple negative) 1.71% (1.38 to 2.09%)
  1. The recent treatment era included 198,496 women diagnosed with a first primary breast cancer between 2004 and 2015 and 3179 CBC cases developed through 2016. Women with contralateral prophylactic mastectomies or unknown type of surgery were excluded from all estimates of cumulative incidence
  2. SEER, Surveillance, Epidemiology, and End Results; CI, confidence interval; ER, estrogen-receptor; HER2, human epidermal growth factor receptor 2; HR, hormone receptor; PR, progesterone receptor
  3. aCumulative incidence was calculated from the index date (the first 12 months after the initial breast cancer diagnosis were excluded)
  4. bHER2-status and breast cancer subtype were estimated in a subgroup of women diagnosed with a first cancer between 2010 and 2015 and followed through 2016 (N = 100,153; CBC = 762; overall 5-year cumulative incidence = 1.34% (1.23–1.45%)
  5. cHR+ = ER+ and/or PR+; HR− = ER− and PR−