Risk of breast cancer associated with current use of combined oral contraceptive preparations and use for 5 years or longer immediately before reference datea
| Controls | Cases | ||||
|---|---|---|---|---|---|
| (n = 882) | (n = 985) | ||||
| n (%) | n (%) | ORb | 95% CI | Pe | |
| Current use and duration of use in the prior 5 years | |||||
| Never use | 103 (11.7) | 119 (12.1) | 1.0 | (ref) | |
| Current use | 144 (16.3) | 201 (20.4) | 1.3 | (0.9–1.8) | |
| ≥5 years | 54 (6.1) | 97 (9.8) | 1.6 | (1.1–2.5)c | |
| Estrogen dosed | 0.44 | ||||
| Low | |||||
| Current use | 16 (1.8) | 29 (3.0) | 1.5 | (0.8–3.0) | |
| ≥5 years | 6 (0.7) | 15 (1.5) | 2.2 | (0.8–6.0) | |
| Moderate | |||||
| Current use | 96 (10.9) | 149 (15.2) | 1.4 | (1.0–2.0) | |
| ≥5 years | 40 (4.5) | 67 (6.8) | 1.5 | (0.9–2.4) | |
| Progestin group | 0.28 | ||||
| Estrane progestins | |||||
| Current use | 45 (5.1) | 67 (6.9) | 1.4 | (0.9–2.2) | |
| ≥5 years | 19 (2.2) | 26 (2.6) | 1.3 | (0.7–2.4) | |
| Norethindrone | |||||
| Current use | 30 (3.4) | 42 (4.3) | 1.3 | (0.7–2.2) | |
| ≥5 years | 15 (1.7) | 17 (1.7) | 1.1 | (0.5–2.2) | |
| Norethindrone acetate | |||||
| Current use | 11 (1.2) | 23 (2.3) | 1.9 | (0.9–4.2) | |
| Gonane progestins | |||||
| Current use | 63 (7.2) | 94 (9.6) | 1.3 | (0.9–2.0) | |
| ≥5 years | 22 (2.5) | 49 (5.0) | 1.9 | (1.1–3.4)c | |
| Levonorgestrel | |||||
| Current use | 19 (2.2) | 33 (3.4) | 1.5 | (0.8–2.9) | |
| ≥5 years | 9 (1.0) | 18 (1.8) | 1.8 | (0.8–4.2) | |
| Norgestimate | |||||
| Current use | 28 (3.2) | 35 (3.6) | 1.1 | (0.6–2.0) | |
| ≥5 years | 7 (0.8) | 15 (1.5) | 1.9 | (0.7–4.8) | |
| Desogestrel | |||||
| Current use | 15 (1.7) | 12 (1.2) | 0.7 | (0.3–1.6) | |
| Other progestin | |||||
| Drospirenone | |||||
| Current use | 9 (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).