Table 3.
Recent oral contraceptive use and invasive breast cancer risk by estrogen receptor status
| Controls (n=21952) No. (%) |
All Cases (n=1102) No. (%) |
OR (95% CI)* | Controls (n=14704) No. (%) |
ER+ Cases‡ (n=738) No. (%) |
OR (95% CI)* | Controls (n=5433) No. (%) |
ER−Cases‡ (n=273) No. (%) |
OR (95% CI)* | |
|---|---|---|---|---|---|---|---|---|---|
| Combined OC use† | |||||||||
| Never/former use | 19953 (90.9) | 957 (86.8) | Reference | 13394 (91.1) | 637 (86.3) | Reference | 4889 (90.0) | 240 (87.9) | Reference |
| Recent use | 1999 (9.1) | 145 (13.2) | 1.5 (1.3–1.9) | 1310 (8.9) | 101 (13.7) | 1.7 (1.3–2.1) | 544 (10.0) | 33 (12.1) | 1.2 (0.8–1.8) |
| Total number of combined OC hormone pills | |||||||||
| <190 | 899 (4.1) | 50 (4.5) | 1.2 (0.9–1.6) | 582 (4.0) | 33 (4.5) | 1.2 (0.8–1.8) | 254 (4.7) | 14 (5.1) | 1.1 (0.6–2.0) |
| 190+ | 1082 (4.9) | 93 (8.5) | 1.8 (1.5–2.3) | 714 (4.9) | 66 (9.0) | 2.0 (1.5–2.6) | 288 (5.3) | 19 (7.0) | 1.4 (0.8–2.2) |
| Missing | 18 | 2 | 14 | 2 | 2 | 0 | |||
| p for trend§ | <0.001 | <0.001 | 0.16 | ||||||
Abbreviations: CI, confidence interval; ER, estrogen receptor; OC, oral contraceptive; OR, odds ratio.
All ORs are implicitly adjusted for the matching factors (age, year, months of enrollment prior to reference date, and medical chart availability).
Recent use is defined as filling at least one combined OC script in the year prior to reference date.
91 cases were excluded because of unknown ER status. Cases with borderline ER results were coded as positive (n=4). There was no statistically significant difference between recent OC use and risk of ER+ compared to ER− breast cancer (p=0.15).
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).