The Women's Health Initiative (WHI) enrolled approximately 27,000
predominantly healthy postmenopausal women in two substudies to assess the risks
and benefits of either the use of daily oral conjugated estrogens (CE 0.625 mg)
alone or in combination with medroxyprogesterone acetate (MPA 2.5 mg) compared
to placebo in the prevention of certain chronic diseases. The primary endpoint
was the incidence of coronary heart disease (CHD) (nonfatal myocardial
infarction [MI], silent MI and CHD death), with invasive breast cancer as the
primary adverse outcome studied. A “global index” included the earliest
occurrence of CHD, invasive breast cancer, stroke, pulmonary embolism (PE),
endometrial cancer (only in the CE/MPA substudy), colorectal cancer, hip
fracture, or death due to other cause. These substudies did not evaluate the
effects of CE or CE/MPA on menopausal symptoms.
The estrogen alone substudy was stopped early because an increased risk of
stroke was observed, and it was deemed that no further information would be
obtained regarding the risks and benefits of estrogen alone in predetermined
primary endpoints. Results of the estrogen alone substudy, which included 10,739
women (average 63 years of age, range 50 to 79 years of age; 75.3 percent White,
15.1 percent Black, 6.1 percent Hispanic, 3.6 percent Other), after an average
follow-up of 6.8 years are presented in Table 5.
For those outcomes included in the WHI “global index” that reached
statistical significance, the absolute excess risk per 10,000 women-years in the
group treated with CE alone was 12 more strokes, while the absolute risk
reduction per 10,000 women-years was 6 fewer hip fractures. The absolute excess
risk of events included in the “global index” was a non-significant 2 events per
10,000 women-years. There was no difference between the groups in terms of
all-cause mortality [see Warnings and Precautions (5)].
Final centrally adjudicated results for CHD events and centrally adjudicated
results for invasive breast cancer incidence from the estrogen alone substudy,
after an average follow-up of 7.1 years, reported no overall difference for
primary CHD events (nonfatal MI, silent MI and CHD death) and invasive breast
cancer incidence in women receiving CE alone compared to placebo (see Table 5).2,4
Centrally adjudicated results for stroke events from the estrogen alone
substudy, after an average follow-up of 7.1 years, reported no significant
differences in distribution of stroke subtypes or severity, including fatal
strokes, in women receiving CE alone compared to placebo. Estrogen alone
increased the risk for ischemic stroke, and this excess risk was present in all
subgroups of women examined (see Table 5).1
The estrogen plus progestin substudy was also stopped early. According to the
predefined stopping rule, after an average follow-up of 5.2 years of treatment,
the increased risk of breast cancer and cardiovascular events exceeded the
specified benefits included in the “global index.” The absolute excess risk of
events included in the “global index” was 19 per 10,000 women-years (relative
risk [RR] 1.15, 95 percent nCI, 1.03-1.28).
For those outcomes included in the WHI “global index” that reached
statistical significance after 5.6 years of follow-up, the absolute excess risks
per 10,000 women-years in the group treated with CE/MPA were 6 more CHD events,
7 more strokes, 10 more PEs, and 8 more invasive breast cancers, while the
absolute risk reduction per 10,000 women-years were 7 fewer colorectal cancers
and 5 fewer hip fractures [see Warnings and Precautions (5)].
Results of the estrogen plus progestin substudy, which included 16,608 women
(average 63 years of age, range 50 to 79 years of age; 83.9 percent White, 6.5
percent Black, 5.4 percent Hispanic, 3.9 percent Other) are presented in Table 6. These results reflect centrally adjudicated data after
an average follow-up of 5.6 years.
Table 5. Relative and Absolute Risk Seen in the Estrogen Alone Substudy
of WHI | Event | Relative Risk CE vs. Placebo (95% nCIa) | Placebo (n = 5,429) | CE
(n = 5,310) |
|---|
| Absolute Risk per 10,000 Women-Years |
|---|
CHD eventsb Non-fatal MIb CHD deathb | 0.95 (0.79-1.16) 0.91 (0.73-1.14) 1.01
(0.71-1.43) | 56 43 16 | 53 40 16 |
Strokeb Ischemicb | 1.37 (1.09-1.73) 1.55 (1.19-2.01) | 33 25 | 45 38 |
| Deep vein thrombosisb,d | 1.47 (1.06-2.06) | 15 | 23 |
| Pulmonary embolismb | 1.37 (0.90-2.07) | 10 | 14 |
| Invasive breast cancerb | 0.80 (0.62-1.04) | 34 | 28 |
| Colorectal cancerc | 1.08 (0.75-1.55) | 16 | 17 |
| Hip fracturec | 0.61 (0.41-0.91) | 17 | 11 |
| Vertebral fracturesc,d | 0.62 (0.42-0.93) | 17 | 11 |
| Total fracturesc,d | 0.70 (0.63-0.79) | 195 | 139 |
| Death due to other causes
| 1.08 (0.88-1.32) | 50 | 53 |
| Overall mortalityc,d | 1.04 (0.88-1.22) | 78 | 81 |
| Global indexc,f | 1.01 (0.91-1.12) | 190 | 192
|
a Nominal confidence intervals
unadjusted for multiple looks and multiple comparisons.
b Results are based on centrally
adjudicated data for an average follow-up of 7.1 years.
c Results are based on an average
follow-up of 6.8 years.
d Not included in global
index.
e All deaths, except from breast
or colorectal cancer, definite/probable CHD, PE or cerebrovascular disease.
f A subset of the events was
combined in a “global index,” defined as the earliest occurrence of CHD events,
invasive breast cancer, stroke, pulmonary embolism, endometrial cancer,
colorectal cancer, hip fracture, or death due to other causes.