Table 2.

Risk of invasive breast cancer among BRCA mutation carriers according to oral contraceptive use, by BRCA mutation status for all subjects (under 50 years of age)

BRCA1 mutation carriers
BRCA2 mutation carriers
Cases* (n = 195), n (%)Controls* (n = 302), n (%)OR (95% CI)Cases* (n = 128), n (%)Controls* (n = 179), n (%)OR (95% CI)
Oral contraceptive use for ≥1 y
    No49 (25)86 (29)1.0019 (15)45 (26)1.00
    Yes146 (75)214 (71)0.77 (0.53-1.12)109 (85)132 (74)1.62 (0.90-2.92)
Duration of use (y)
    <149 (25)86 (29)1.0019 (15)45 (26)1.00
    1-440 (21)84 (28)0.68 (0.43-1.08)24 (19)45 (26)1.16 (0.58-2.34)
    ≥5102 (54)128 (43)0.80 (0.54-1.18)84 (66)83 (48)2.06 (1.08-3.94)
    Trend per year0.99 (P = 0.62)1.08 (P = 0.008)
Age at first use (y)
    Nonusers49 (26)86 (29)1.0019 (15)45 (26)1.00
    <2087 (45)129 (44)0.79 (0.53-1.17)73 (57)76 (45)1.82 (0.96-3.44)
    ≥2058 (29)80 (27)0.81 (0.51-1.26)36 (28)49 (29)1.65 (0.87-3.16)
    Trend per year1.00 (P = 0.94)0.93 (P = 0.41)
Time since last use (y)
    Nonusers49 (26)86 (29)1.0019 (15)45 (26)1.00
    ≥1068 (35)70 (24)1.00 (0.64-1.57)48 (38)50 (30)1.92 (0.97-3.82)
    <1075 (39)138 (47)0.63 (0.42-0.95)60 (47)75 (44)1.62 (0.91-2.87)
    Trend per year1.04 (P = 0.002)1.02 (P = 0.34)
Years of use before first full-term§ pregnancy
    <173 (38)121 (41)1.0030 (24)83 (47)1.00
    1-338 (20)73 (25)0.82 (0.54-1.24)25 (20)36 (21)1.53 (0.86-2.74)
    ≥479 (42)102 (34)0.91 (0.62-1.32)72 (56)56 (32)3.46 (2.10-5.70)
    Trend per year0.99 (P = 0.73)1.16 (P < 0.0001)
Years of use before age 30
    <151 (27)89 (30)1.0021 (16)53 (30)1.00
    1-36 (3)25 (8)0.42 (0.20-0.85)5 (4)13 (7)1.49 (0.51-4.34)
    ≥4134 (70)183 (62)0.93 (0.64-1.35)101 (80)109 (63)2.20 (1.26-3.85)
    Trend per year1.00 (P = 0.93)1.08 (P = 0.008)
  • * The totals for the different variables may not equal to the total number of subjects in a category because of missing data.

  • Adjusted for age, study site, family history, and number of full-term pregnancies.

  • Never or <1 year of use.

  • § Livebirths and stillbirths.