Table 3.

Use of tamoxifen and risk of second primary contralateral breast cancer by hormone receptor status

Use of tamoxifenControls (n = 674)Contralateral cases (n = 358)OR * (95% CI)
n (%)n (%)
All contralateral cases
    Never212 (31.4)144 (40.2)1.0 (Reference)
    Ever462 (68.6)214 (59.8)0.6 (0.5–0.8)
    <1 y86 (12.8)48 (13.4)0.8 (0.5–1.2)
    1–4 y258 (38.3)113 (31.6)0.6 (0.4–0.8)
    ≥5 y115 (17.1)51 (14.2)0.6 (0.4–0.8)
ER+ contralateral cases
    Never178 (32.0)132 (44.8)1.0 (Reference)
    Ever378 (68.0)165 (55.2)0.5 (0.4–0.7)
    <1 y65 (11.6)37 (12.5)0.7 (0.4–1.2)
    1–4 y209 (37.6)90 (30.3)0.5 (0.4–0.8)
    ≥5 y98 (17.6)36 (12.1)0.4 (0.3–0.7)
ER+/PR+ contralateral cases
    Never149 (34.9)111 (48.7)1.0 (Reference)
    Ever278 (65.1)117 (51.3)0.5 (0.4–0.7)
    <1 y52 (12.2)32 (14.0)0.7 (0.4–1.3)
    1–4 y155 (36.3)58 (25.4)0.5 (0.3–0.7)
    ≥5 y66 (15.5)25 (11.0)0.5 (0.3–0.8)
ER− contralateral cases
    Never27 (27.8)10 (20.0)1.0 (Reference)
    Ever70 (72.2)40 (80.0)1.6 (0.7–3.3)
    <1 y16 (16.5)10 (20.0)1.1 (0.3–3.8)
    1–4 y40 (41.2)16 (32.0)0.7 (0.3–1.9)
    ≥5 y14 (14.4)14 (28.0)4.4 (1.03–19.0)
ER−/PR− contralateral cases
    Never25 (30.5)10 (22.7)1.0 (Reference)
    Ever57 (69.5)34 (77.3)1.2 (0.5–2.9)
    <1 y14 (17.0)8 (18.2)0.9 (0.3–3.2)
    1–4 y34 (41.5)15 (34.1)0.8 (0.3–2.2)
    ≥5 y9 (11.0)11 (25.0)5.9 (1.1–32.6)
  • NOTE: Ever users of other forms of adjuvant hormonal therapy were excluded from all analyses presented in this table. The 11 cases with missing ER status and their matched 23 matched controls were excluded from the ER-specific analyses, and the 90 cases with other/missing ER/PR status and their matched 180 matched controls were excluded from the ER/PR-specific analyses.

  • * ORs and 95% CIs were estimated using conditional logistic regression and are adjusted for radiation therapy.