Table 3

HRs and 95% CIs for the association between physical activity and the risk of a second breast cancer diagnosis: WISC DCIS cohort, 1997–2010

All second breast cancer diagnosesInvasive second breast cancer diagnoses
Prediagnosis (N = 1,925)Postdiagnosis (N = 1,903)bPrediagnosis (N = 1,925)Postdiagnosis (N = 1,903)b
Second diagnosisHR (95% CI)aPtrendcHR (95% CI)aPtrendcSecond diagnosisHR (95% CI)aPtrendcHR (95% CI)aPtrendc
Total physical activity (h/wk)
 No activity441.00 (Ref.)0.661.00 (Ref.)0.90171.00 (Ref.)0.151.00 (Ref)0.08
 >0–2370.97 (0.62–1.52)0.37 (0.12–1.07)151.02 (0.50–2.08)1.05 (0.20–5.58)
 >2–5541.16 (0.77–1.75)0.92 (0.47–1.81)170.93 (0.47–1.86)1.75 (0.55–5.81)
 5+270.81 (0.49–1.33)0.89 (0.36–2.22)80.60 (0.25–1.43)1.78 (0.41–7.61)
 Continuous per 1 h/wk1620.98 (0.94–1.02)0.97 (0.88–1.08)570.98 (0.91–1.05)1.03 (0.90–1.17)
BCS with or without radiation (h/wk)
 No activity271.00 (Ref.)0.541.00 (Ref.)0.58111.00 (Ref.)0.141.00 (Ref)0.24
 >0–2271.07 (0.62–1.84)0.31 (0.07–1.40)100.95 (0.39–2.32)1.98 (0.27–14.0)
 >2–5361.17 (0.70–1.96)1.41 (0.61–3.22)110.95 (0.39–2.27)3.91 (0.82–19.5)
 5+170.76 (0.40–1.42)1.24 (0.39–3.92)60.70 (0.25–2.00)2.78 (0.37–22.0)
 Continuous per 1 h/wk1070.97 (0.92–1.02)0.99 (0.88–1.12)381.00 (0.92–1.08)1.05 (0.90–1.28)
Ipsilateral mastectomy (h/wk)
 No activity151.00 (Ref.)0.181.00 (Ref.)0.076dd
 >0–2101.03 (0.45–2.35)0.40 (0.07–2.23)5
 >2–5120.84 (0.37–1.88)0.13 (0.01–1.57)3
 5+80.72 (0.30–1.75)0.06 (0.00–1.51)1
 Continuous per 1 h/wk450.97 (0.88–1.06)0.67 (0.45–1.02)15
  • aAdjusted for age at diagnosis, mode of detection, treatment type, postmenopausal hormone use, tamoxifen use, year of diagnosis, tumor size, tumor grade, and remaining lifestyle factors.

  • bPostdiagnosis results are additionally adjusted for prediagnosis levels of each lifestyle factor.

  • cP is for linear trend across categories.

  • dLow numbers of invasive second breast cancer diagnoses among women treated with ipsilateral mastectomy precluded separate analysis of this subgroup.