Table 2.

Risk of invasive breast cancer associated with oral contraceptive use, by BRCA1 and BRCA2 mutation carrier status

Controls (n = 815)Cases
Mutation carriers
Noncarriers (n = 1,073)*
BRCA1 (n = 47)
BRCA2 (n = 36)
n (%)OR (95% CI)n (%)OR (95% CI)n (%)OR (95% CI)
Oral contraceptive use
    No110 (14)16 (34)1.00 (—)5 (14)1.00 (—)152 (14)1.00 (—)
    Yes701 (86)31 (66)0.22 (0.10-0.49)31 (86)1.02 (0.34-3.09)920 (86)0.93 (0.69-1.24)
Duration of use (y)
    <1 or none110 (14)16 (34)1.00 (—)5 (14)1.00 (—)152 (14)1.00 (—)
    1-4196 (24)10 (21)0.25 (0.09-0.70)8 (22)0.97 (0.26-3.56)202 (19)0.76 (0.54-1.07)
    5-9256 (32)12 (26)0.22 (0.09-0.58)14 (39)1.34 (0.41-4.45)337 (32)0.97 (0.70-1.34)
    ≥10248 (31)9 (19)0.20 (0.08-0.54)9 (25)0.73 (0.20-2.65)378 (35)1.02 (0.74-1.41)
Age at first use (y)
    Nonuser110 (14)16 (34)1.00 (—)5 (14)1.00 (—)152 (14)1.00 (—)
    <20461 (66)22 (71)0.26 (0.11-0.62)26 (84)1.40 (0.44-4.25)652 (71)1.01 (0.75-1.37)
    ≥20240 (34)9 (29)0.16 (0.06-0.46)5 (16)0.40 (0.10-1.71)267 (29)0.76 (0.55-1.06)
Time since last use (y)
    Nonuser110 (14)16 (34)1.00 (—)5 (14)1.00 (—)152 (14)1.00 (—)
    <5410 (51)14 (30)0.16 (0.07-0.40)10 (29)0.43 (0.12-1.53)510 (50)0.85 (0.63-1.16)
    5-9148 (18)11 (23)0.38 (0.14-1.06)13 (37)2.80 (0.77-10.2)200 (19)0.96 (0.67-1.36)
    ≥10143 (18)6 (13)0.32 (0.09-1.10)7 (20)2.01 (0.47-8.60)166 (16)0.91 (0.63-1.31)
Year of first use
    Nonuser110 (14)16 (34)1.00 (—)5 (14)1.00 (—)152 (14)1.00 (—)
    ≤197577 (9)6 (13)1.72 (0.41-7.23)6 (17)4.18 (0.80-21.9)228 (21)3.10 (2.01-4.61)
    >1975624 (77)25 (53)0.18 (0.08-0.42)25 (69)0.92 (0.30-2.84)691 (65)0.74 (0.55-0.99)
  • * Includes 794 cases who tested negative for mutations in both BRCA1 and BRCA2, 18 who tested negative for mutations in one of these genes but were not tested for mutations in the other gene, and 261 who were not tested for mutations in either gene.

  • OR (adjusted for study location/period, reference age, family history, education, marital status, country of birth, age at menarche, and number of full-term pregnancies) and corresponding 95% CI.

  • Never used oral contraceptives or used for <1 year.