Table 4.

Risk of invasive breast cancer associated with year of first use of oral contraceptives, by BRCA1 and BRCA2 mutation carrier status, first-degree family history of breast cancer, and parity

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)
Year first used oral contraceptives
Women with no affected first-degree relatives
    Nonuser§106 (14)11 (42)1.00 (—)2 (9)1.00 (—)127 (13)1.00 (—)
    ≤197573 (9)5 (19)1.61 (0.43-6.05)3 (14)3.07 (0.46-20.5)202 (21)3.23 (2.10-4.96)
    >1975595 (77)10 (38)0.16 (0.06-0.39)17 (77)1.34 (0.30-5.93)627 (66)0.79 (0.58-1.08)
Women with an affected first-degree relative
    Nonuser§4 (12)5 (24)1.00 (—)3 (21)1.00 (—)24 (21)1.00 (—)
    ≤19754 (12)1 (5)0.22 (0.01-3.94)3 (21)2.08 (0.15-29.6)26 (23)1.37 (0.21-8.71)
    >197525 (76)15 (71)0.42 (0.08-2.10)8 (57)0.49 (0.07-3.62)64 (56)0.25 (0.06-0.99)
Nulliparous women
    Nonuser§51 (18)8 (47)1.00 (—)3 (33)1.00 (—)53 (16)1.00 (—)
    197515 (5)0 (0)2 (22)2.81 (0.28-27.7)48 (14)3.99 (1.73-9.17)
    >1975219 (77)9 (53)0.27 (0.10-0.76)4 (44)0.20 (0.04-1.01)237 (70)0.97 (0.60-1.57)
Parous women
    Nonuser§59 (11)8 (27)1.00 (—)2 (7)1.00 (—)99 (14)1.00 (—)
    ≤197562 (12)6 (20)0.88 (0.27-2.84)4 (15)2.52 (0.42-15.0)180 (25)2.40 (1.47-3.90)
    >1975405 (77)16 (53)0.27 (0.11-0.67)21 (78)1.46 (0.33-6.43)454 (62)0.60 (0.41-0.87)
  • * 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.

  • Age-adjusted OR and corresponding 95% CI; categories of age were collapsed where necessary so that at least one case was included in each category.

  • OR adjusted for study location/period, reference age (with categories collapsed where necessary so that at least one case was included in each category), family history (where appropriate), education, marital status, country of birth, age at menarche, and number of full-term pregnancies (where appropriate) and corresponding 95% CI.

  • § Never, or use for <1 year.