Table 2.
Intention-to-treat average hazard ratios (HR) and risk differences (RD) (cases per 100 women) and their 95% confidence intervals (CIs) of invasive breast cancer, Women’s Health Initiative estrogen-plus-progestin (E+P) randomized triala
| Follow-up period | |||
|---|---|---|---|
| 0–2 years | 0–6 years | 0–8 years | |
| Overall | |||
| No. of cases; E+P/placebo | 38/51 | 181/140 | 198/149 |
| HR (95% CI) | 0.71 (0.46 to 1.08) | 1.23 (0.98 to 1.53) | 1.25 (1.01 to 1.54) |
| RD (95% CI) | −0.16 (−0.37 to 0.05) | 0.53 (0.03 to 1.03) | 0.83 (−0.03 to 1.69) |
| Prior hormone use | |||
| No | |||
| No. of cases; E+P/placebo | 22/36 | 127/112 | 140/120 |
| HR (95% CI) | 0.59 (0.34 to 1.00) | 1.08 (0.84 to 1.39) | 1.10 (0.86 to 1.40) |
| RD (95% CI) | −0.25 (−0.47 to −0.02) | 0.27 (−0.33 to 0.87) | 0.46 (−0.63 to 1.55) |
| Yes | |||
| No. of cases; E+P/placebo | 16/15 | 54/28 | 58/29 |
| HR (95% CI) | 1.02 (0.51 to 2.07) | 1.82 (1.15 to 2.87) | 1.87 (1.20 to 2.92) |
| RD (95% CI) | 0.11 (−0.36 to 0.57) | 1.31 (0.47 to 2.15) | 1.84 (0.62 to 3.06) |
| Years since menopauseb | |||
| < 10 | |||
| No. of cases; E+P/placebo | 15/18 | 52/40 | 55/43 |
| HR (95% CI) | 0.80 (0.41 to 1.60) | 1.26 (0.83 to 1.90) | 1.23 (0.83 to 1.84) |
| RD (95% CI) | −0.11 (−0.47 to 0.24) | 0.42 (−0.37 to 1.20) | 0.48 (−0.61 to 1.57) |
| ≥ 10 | |||
| No. of cases; E+P/placebo | 20/31 | 109/91 | 118/95 |
| HR (95% CI) | 0.63 (0.36 to 1.10) | 1.17 (0.89 to 1.55) | 1.21 (0.93 to 1.59) |
| RD (95% CI) | −0.22 (−0.51 to 0.07) | 0.57 (−0.09 to 1.24) | 1.09 (−0.38 to 2.57) |
| Age group | |||
| < 60 | |||
| No. of cases; E+P/placebo | 10/15 | 47/35 | 52/39 |
| HR (95% CI) | 0.62 (0.28 to 1.38) | 1.25 (0.81 to 1.94) | 1.23 (0.81 to 1.86) |
| RD (95% CI) | −0.16 (−0.47 to 0.15) | 0.41 (−0.28 to 1.10) | −0.19 (−1.51 to 1.14) |
| ≥ 60 | |||
| No. of cases; E+P/placebo | 28/36 | 134/105 | 146/110 |
| HR (95% CI) | 0.74 (0.45 to 1.22) | 1.22 (0.94 to 1.57) | 1.25 (0.98 to 1.61) |
| RD (95% CI) | −0.15 (−0.42 to 0.12) | 0.64 (0.01 to 1.27) | 1.46 (0.39 to 2.53) |
a
Average hazard ratios in a given period (e.g., 0–2 years) were estimated over the entire period, while risk differences were estimated at the end of the period
b
1,420 women (827 in estrogen-plus-progestin group and 593 in placebo group) had missing years since menopause