Table 2.

Estrogen plus progestin use and endometrial cancer

No hormone therapy
Only estrogen plus progestin*
Only sequential estrogen plus progestin
Only continuous estrogen plus progestin
No./person-yearsRR (95% CI)No./person-yearsRR (95% CI)No./person-yearsRR (95% CI)No./person-yearsRR (95% CI)
No Use
Any use168/209,1961.0 (Reference)68/35,3942.6 (1.9-3.5)32/15,5653.0 (2.0-4.6)15/8,1982.3 (1.3-4.0)
Duration of use (y)
    <223/16,7792.1 (1.3-3.3)5/5,8901.3 (0.5-3.2)3/3,8401.1 (0.3-3.4)
    2-313/7,2242.7 (1.5-4.9)7/3,9072.4 (1.1-5.3)6/2,1333.9 (1.7-9.2)
    4-59/5,1862.4 (1.2-4.8)5/2,6582.5 (0.99-6.2)3/1,3072.9 (0.9-9.4)
    ≥623/6,2054.4 (2.7-7.1)15/3,1105.7 (3.2-10.2)3/9184.2 (1.3-13.6)
    P<0.001<0.001<0.001
    Excess RR per year0.38 (0.20-0.64)0.45 (0.22-0.80)0.52 (0.15-1.13)
Recency of use
    Current use31/16,9142.6 (1.7-3.9)18/82713.1 (1.8-5.3)8/4,8682.3 (1.1-4.9)
    <5 y ago8/6,7391.6 (0.8-3.4)
    5-9 y ago5/2,4942.5 (0.99-6.1)10/61322.1 (1.1-4.2)5/2,6222.4 (0.97-6.1)
    ≥10 y ago5/2,0123.1 (1.3-7.8)
  • * Does not include 55 carcinomas and 24,503 person-years (RR, 2.8; 95% CI, 2.0-3.8) among women who used estrogen plus progestin after using unopposed estrogen therapy. Includes women who used both sequential estrogen plus progestin and continuous estrogen plus progestin (5 carcinomas and 3,718 person-years; RR, 1.6; 95% CI, 0.6-4.0) and unknown estrogen plus progestin regimen (15 carcinomas and 7,643 person-years; RR, 2.8; 95% CI, 1.6-4.8).

  • Reference group for all exposures. All RRs adjusted for attained age, calendar time, household income, age at menarche, parity, duration of oral contraceptive use, current smoking, and BMI.

  • Unknown recency: 19 carcinomas and 7,250 person-years; RR, 3.5; 95% CI, 2.2-5.8. For sequential estrogen plus progestin and continuous estrogen plus progestin, comparison is no use versus current use and former use.