Table 3.

Risk of invasive breast cancer according to oral contraceptive use for women <40 years of age, by BRCA mutation carrier status

BRCA1 mutation carriers
BRCA2 mutation carriers
Cases* (n = 111), n (%)Controls* (n = 185), n (%)OR (95% CI)Cases* (n = 71), n (%)Controls* (n = 94), n (%)OR (95% CI)
Oral contraceptive use for ≥1 y
    No26 (24)49 (26)1.0010 (14)26 (28)1.00
    Yes85 (76)136 (74)0.64 (0.35-1.16)61 (86)68 (72)1.29 (0.61-2.76)
Duration of use (y)
    <126 (24)49 (26)1.0010 (14)26 (28)1.00
    1-424 (22)56 (31)0.61 (0.31-1.17)10 (14)20 (21)0.79 (0.26-2.37)
    ≥558 (54)79 (43)0.61 (0.32-1.16)50 (72)48 (51)1.45 (0.64-3.27)
    Trend per year0.97 (P = 0.27)1.06 (P = 0.24)
Age at first use (y)
    Nonusers26 (24)49 (26)1.0010 (14)26 (28)1.00
    <2064 (58)84 (47)0.84 (0.45-1.55)47 (66)46 (50)1.64 (0.77-3.46)
    ≥2020 (18)48 (27)0.45 (0.22-0.92)14 (20)20 (22)0.89 (0.33-2.40)
    Trend per year0.89 (P = 0.08)0.89 (P = 0.11)
Time since last use (y)
    Nonusers26 (24)49 (26)1.0010 (14)26 (28)1.00
    >1024 (22)17 (9)1.10 (0.48-2.53)13 (19)11 (12)0.83 (0.30-2.33)
    <1059 (54)115 (65)0.55 (0.30-1.01)47 (67)55 (60)1.48 (0.70-3.14)
    Trend per year1.06 (P = 0.01)0.95 (P = 0.17)
Years of use before first full-term§ pregnancy
    <137 (35)66 (36)1.0013 (19)35 (37)1.00
    1-321 (20)45 (25)0.71 (0.40-1.28)12 (17)19 (20)0.81 (0.36-1.81)
    ≥449 (45)72 (39)0.69 (0.41-1.16)45 (64)40 (43)2.08 (1.02-4.25)
    Trend per year0.95 (P = 0.21)1.11 (P = 0.01)
Years of use before age 30
    <128 (26)49 (27)1.0011 (16)26 (28)1.00
    1-32 (2)19 (10)0.20 (0.06-0.68)2 (3)4 (4)1.30 (0.15-11.0)
    ≥478 (72)115 (63)0.89 (0.50-1.57)57 (81)64 (68)1.48 (0.68-3.20)
    Trend per year1.00 (P = 0.90)1.03 (P = 0.36)
  • * 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 or stillbirths.