Table 3.

Risk of breast cancer associated with current use of combined oral contraceptive preparations and use for 5 years or longer immediately before reference datea

ControlsCases
(n = 882)(n = 985)
n (%)n (%)ORb95% CIPe
Current use and duration of use in the prior 5 years
 Never use103 (11.7)119 (12.1)1.0(ref)
 Current use144 (16.3)201 (20.4)1.3(0.9–1.8)
  ≥5 years54 (6.1)97 (9.8)1.6(1.1–2.5)c
Estrogen dosed0.44
Low
 Current use16 (1.8)29 (3.0)1.5(0.8–3.0)
  ≥5 years6 (0.7)15 (1.5)2.2(0.8–6.0)
Moderate
 Current use96 (10.9)149 (15.2)1.4(1.0–2.0)
  ≥5 years40 (4.5)67 (6.8)1.5(0.9–2.4)
Progestin group0.28
Estrane progestins
 Current use45 (5.1)67 (6.9)1.4(0.9–2.2)
  ≥5 years19 (2.2)26 (2.6)1.3(0.7–2.4)
 Norethindrone
  Current use30 (3.4)42 (4.3)1.3(0.7–2.2)
   ≥5 years15 (1.7)17 (1.7)1.1(0.5–2.2)
 Norethindrone acetate
  Current use11 (1.2)23 (2.3)1.9(0.9–4.2)
Gonane progestins
 Current use63 (7.2)94 (9.6)1.3(0.9–2.0)
  ≥5 years22 (2.5)49 (5.0)1.9(1.1–3.4)c
 Levonorgestrel
  Current use19 (2.2)33 (3.4)1.5(0.8–2.9)
   ≥5 years9 (1.0)18 (1.8)1.8(0.8–4.2)
 Norgestimate
  Current use28 (3.2)35 (3.6)1.1(0.6–2.0)
   ≥5 years7 (0.8)15 (1.5)1.9(0.7–4.8)
 Desogestrel
  Current use15 (1.7)12 (1.2)0.7(0.3–1.6)
Other progestin
 Drospirenone
  Current use9 (1.0)22 (2.2)2.1(0.9–4.9)

Abbreviations: OC, oral contraceptive; OR, odds ratio; CI, confidence interval.

  • aCurrent use indicates use within the prior year and for ≥6 months. Only exclusive current users of one preparation for 5 years or longer are included in the estrogen and progestin groups for current use for ≥5 years (groups do not add up to the total because of women missing OC preparation information or using multiple preparations in the prior 5 years). Cells with <5 women are not displayed. Among current OC users, 13% controls and 9% cases could not be classified by estrogen dose and/or progestin type.

  • bORs are adjusted for age, year, and race/ethnicity.

  • cP <0.05.

  • dLow dose, <30 μg ethinyl estradiol (EE); moderate dose, 30–35 μg EE or 50 μg mestranol.

  • eP for difference (low versus moderate estrogen dose and estrane versus gonane progestins).