Table 3.

RRs and 95% CIs associated with unopposed estrogen use

Unopposed estrogensCarcinomasPerson-yearsRR (95% CI)*
Ever-use
    No use168209,1961.0 (Reference)
    Unopposed estrogens only16773,8472.7 (2.2-3.4)
    Estrogen, unknown progestins6629,5762.5 (1.8-3.3)
Duration of use (y)
    No use168209,1961.0 (Reference)
    <57152,7151.7 (1.3-2.3)
    5-93811,8394.5 (3.1-6.6)
    ≥10577,58710.7 (7.7-14.9)
        P<0.001
        Excess RR per year0.58 (0.42-0.79)
Time since last use§
    No use168209,1961.0 (Reference)
    Current user639,45110.8 (7.9-14.7)
    Last use <5 y ago2213,6082.5 (1.6-3.9)
    Last use 5-9 y ago2414,4522.2 (1.4-3.4)
    Last use ≥10 y ago4329,4681.5 (1.0-2.1)
  • * Adjusted for attained age, calendar time, household income, age at menarche, parity, duration of oral contraceptive use, current smoking, and BMI.

  • Unknown hormone therapy use accounted for 12 cancers and 21,256 person-years (adjusted RR, 0.75; 95% CI, 0.42-1.35).

  • Restricted to women who never used hormones and women who used unopposed estrogens only. Unknown duration of use accounted for 1 cancer and 1,707 person-years (adjusted RR, 0.78; 95% CI, 0.11-5.62).

  • § Restricted to women who never used hormones and women who used unopposed estrogens only. Current use includes use within the previous year. Unknown time since last use accounted for 15 cancers and 6,869 person-years (adjusted RR, 2.4; 95% CI, 1.4-4.2). Person-year weighed mean durations of unopposed estrogen use were as follows: current users, 5.8 years; last use <5 years ago, 4.1 years; last use 5-9 years ago, 3.5 years; and last use ≥10 years ago, 2.9 years.