Table 5.
Recent oral contraceptive use by estrogen dose and progestin type and invasive breast cancer risk, by all cases (left) and ER positive cases (right)
| Number of pills† | Controls (n=21952) No. (%) |
All Cases (n=1102) No. (%) |
OR (95% CI)* | Controls (n=14704) No. (%) |
ER+ Cases (n=738) No. (%) |
OR (95% CI)* |
|---|---|---|---|---|---|---|
| Never/former use | 19953 (90.9) | 957 (86.8) | Reference | 13394 (91.1) | 637 (86.3) | Reference |
| Low estrogen dose | 367 (1.7) | 18 (1.6) | 1.0 (0.6–1.7) | 256 (1.7) | 14 (1.9) | 1.2 (0.7–2.0) |
| <190 | 228 (1.0) | 11 (1.0) | 1.0 (0.6–1.9) | 155 (1.1) | 10 (1.4) | 1.4 (0.7–2.6) |
| 190+ | 138 (0.6) | 7 (0.6) | 1.1 (0.5–2.3) | 100 (0.7) | 4 (0.5) | 0.9 (0.3–2.3) |
| p for trend‡ | 0.94 | 0.81 | ||||
| Moderate estrogen dose | 1654 (7.5) | 126 (11.4) | 1.6 (1.3–2.0) | 1063 (7.2) | 86 (11.7) | 1.8 (1.4–2.2) |
| <190 | 734 (3.3) | 45 (4.1) | 1.3 (1.0–1.8) | 463 (3.2) | 29 (3.9) | 1.4 (0.9–2.0) |
| 190+ | 919 (4.2) | 81 (7.4) | 1.9 (1.5–2.4) | 600 (4.1) | 57 (7.7) | 2.1 (1.5–2.8) |
| p for trend‡ | <0.001 | <0.001 | ||||
| High estrogen dose | 47 (0.2) | 6 (0.5) | 2.7 (1.1–6.2) | 32 (0.2) | 6 (0.8) | 3.9 (1.6–9.4) |
| p for trend‡ | 0.01 | 0.01 | ||||
| Progestin types§ | ||||||
| Estrane progestin§ | 1472 (6.7) | 111 (10.1) | 1.6 (1.3–2.0) | 973 (6.6) | 76 (10.3) | 1.7 (1.3–2.2) |
| <190 | 741 (3.4) | 43 (3.9) | 1.2 (0.9–1.7) | 487 (3.3) | 28 (3.8) | 1.2 (0.8–1.8) |
| 190+ | 729 (3.3) | 68 (6.2) | 2.0 (1.5–2.6) | 485 (3.3) | 48 (6.5) | 2.1 (1.6–2.9) |
| p for trend‡ | <0.001 | <0.001 | ||||
| Norethindrone | 819 (3.7) | 59 (5.4) | 1.5 (1.2–2.0) | 519 (3.5) | 35 (4.7) | 1.5 (1.0–2.1) |
| <190 | 415 (1.9) | 20 (1.8) | 1.0 (0.7–1.6) | 252 (1.7) | 9 (1.2) | 0.8 (0.4–1.5) |
| 190+ | 403 (1.8) | 39 (3.5) | 2.1 (1.5–2.9) | 267 (1.8) | 26 (3.5) | 2.1 (1.4–3.2) |
| p for trend‡ | <0.001 | <0.001 | ||||
| Norethindrone acetate | 609 (2.8) | 46 (4.2) | 1.6 (1.2–2.2) | 425 (2.9) | 36 (4.9) | 1.8 (1.3–2.6) |
| <190 | 339 (1.5) | 27 (2.5) | 1.7 (1.1–2.5) | 240 (1.6) | 22 (3.0) | 2.0 (1.3–3.1) |
| 190+ | 269 (1.2) | 19 (1.7) | 1.5 (0.9–2.4) | 184 (1.3) | 14 (1.9) | 1.6 (0.9–2.8) |
| p for trend‡ | 0.06 | 0.06 | ||||
| Ethynodiol diacetate | 100 (0.5) | 12 (1.1) | 2.6 (1.4–4.7) | 64 (0.4) | 9 (1.2) | 3.1 (1.5–6.2) |
| <190 | 59 (0.3) | 2 (0.2) | 0.7 (0.2–3.0) | 38 (0.3) | 1 (0.1) | 0.6 (0.1–4.2) |
| 190+ | 41 (0.2) | 10 (0.9) | 5.2 (2.6–10.5) | 26 (0.2) | 8 (1.1) | 6.7 (3.0–15.1) |
| p for trend‡ | <0.001 | <0.001 | ||||
| Gonane progestin§ | 597 (2.7) | 40 (3.6) | 1.4 (1.0–2.0) | 385 (2.6) | 29 (3.9) | 1.6 (1.1–2.4) |
| <190 | 269 (1.2) | 17 (1.6) | 1.4 (0.8–2.3) | 165 (1.1) | 12 (1.6) | 1.6 (0.9–2.9) |
| 190+ | 312 (1.4) | 21 (1.9) | 1.4 (0.9–2.3) | 207 (1.4) | 15 (2.0) | 1.6 (0.9–2.7) |
| p for trend‡ | 0.12 | 0.11 | ||||
| Levonorgestrel | 352 (1.6) | 25 (2.3) | 1.5 (1.0–2.3) | 222 (1.5) | 16 (2.2) | 1.6 (0.9–2.6) |
| <190 | 141 (0.6) | 14 (1.3) | 2.2 (1.2–3.8) | 80 (0.5) | 9 (1.2) | 2.4 (1.2–4.9) |
| 190+ | 211 (1.0) | 11 (1.0) | 1.1 (0.6–2.1) | 142 (1.0) | 7 (1.0) | 1.1 (0.5–2.3) |
| p for trend‡ | 0.45 | 0.61 | ||||
| Norgestimate | 188 (0.9) | 10 (0.9) | 1.2 (0.6–2.2) | 130 (0.9) | 8 (1.1) | 1.4 (0.6–2.8) |
| <190 | 112 (0.5) | 4 (0.4) | 0.8 (0.3–2.1) | 80 (0.5) | 4 (0.5) | 1.1 (0.4–3.1) |
| 190+ | 76 (0.4) | 6 (0.5) | 1.7 (0.7–3.9) | 50 (0.3) | 4 (0.5) | 1.7 (0.6–4.9) |
| p for trend‡ | 0.22 | 0.20 | ||||
Abbreviations: CI, confidence interval; EE, ethinyl estradiol; ER, estrogen receptor; mcg, micrograms; ME, mestranol; OC, oral contraceptive; OR, odds ratio.
All ORs are implicitly adjusted for the matching factors.
Recent use is defined as filling at least one combined OC script in the year prior to reference date. Includes mono- and triphasic OCs. Categories are not mutually exclusive and numbers may not add up to column totals because of missing values. Low estrogen dose=20 mcg EE, moderate estrogen dose=30–35 mcg EE or 50 mcg ME, and high estrogen dose=50 mcg EE or 80 mcg ME.
P for trend in the prior year (maximum number of pills=365) using the continuous linear variable and a reference group comprised of never/former OC users.
Estrane progestins include norethindrone, norethindrone acetate, and ethynodiol diacetate. Gonane progestins include levonorgestrel, norgestimate, norgestrel, and desogestrel. ORs for recent use of norgestrel and desogestrel are not displayed because <5 cases were exposed to these progestin types.