Table 2.

Distribution of established breast cancer etiologic factors among 804 breast cancer cases and 2,502 controls participating in the Polish Breast Cancer Study

Subject characteristicsControls* (N = 2,502)Breast cancer cases*,
Luminal A (n = 552)Luminal B (n = 48)HER2-expressing (n = 61)Basal-like (n = 95)Unclassified (n = 48)P
Age, mean (SD)55.9 (10.1)56.3 (9.9)56.3 (9.4)56.0 (10.6)53.7 (10.9)57.3 (9.9)0.27
Education, no. (%)
    High school or lower1,900 (76)343 (63)35 (73)44 (72)65 (69)34 (71)
    College or higher586 (24)204 (37)13 (27)17 (28)29 (31)14 (29)0.25
Age at menarche, mean (SD)13.7 (1.7)13.5 (1.7)13.4 (1.9)13.7 (1.9)13.0 (1.6)13.7 (1.3)0.003
Age at first full term birth, mean (SD)23.6 (4.2)24.6 (4.5)23.8 (4.1)23.5 (3.7)23.7 (4.0)24.2 (3.9)0.002
Number of full-term births, no. (%)
    0281 (11)99 (18)7 (15)11 (18)9 (9)6 (13)
    1746 (30)185 (33)18 (37)19 (31)36 (38)13 (27)0.36
    ≥21,475 (59)268 (49)23 (48)31 (51)50 (53)29 (60)0.29
Menopausal status, no. (%)
    Premenopausal715 (29)144 (26)12 (25)12 (20)36 (38)13 (27)
    Postmenopausal1,682 (67)366 (66)33 (69)47 (77)56 (59)33 (69)0.13
    Unclear103 (4)42 (8)3 (6)2 (3)3 (3)2 (4)Not determined
Age at menopause, mean (SD)49.2 (5.0)49.8 (4.4)49.6 (4.6)49.3 (4.7)49.4 (4.0)51.2 (4.3)0.07
BMI among premenopausal women, mean (SD)26.4 (5.1)24.8 (4.0)25.6 (5.8)23.5 (4.1)27.1 (4.9)27.2 (4.8)0.003
BMI among postmenopausal women, mean (SD)28.6 (5.4)28.3 (5.6)28.7 (5.7)28.2 (5.0)27.8 (5.4)28.9 (6.6)0.80
Oral HRT use among postmenopausal women, no. (%)
    Never user1,323 (83)260 (76)28 (88)38 (83)42 (81)20 (65)
    Current/recent use of combined HRT93 (6)45 (13)1 (3)4 (9)4 (7)5 (16)0.25
    Past use of combined HRT75 (5)19 (5)0 (0)2 (4)3 (6)2 (6)Not determined
    Use of estrogen or progesterone alone104 (6)20 (6)3 (9)2 (4)3 (6)4 (13)Not determined
Breast cancer in first-degree relatives
    No2,356 (94)496 (90)43 (90)53 (87)80 (84)45 (94)
    Yes146 (6)55 (10)5 (10)8 (13)15 (16)3 (6)0.37
Previous benign breast disease, no. (%)
    No2,323 (94)476 (89)43 (91)55 (92)87 (95)43 (93)
    Yes157 (6)61 (11)4 (9)5 (8)5 (5)3 (7)0.39
  • * Numbers for some factors might be less than the total numbers due to missing data.

  • Molecular subtypes were defined as luminal A (ER+ and/or PR+, HER2−), luminal B (ER+ and/or PR+, HER2+), HER2 (HER2+, ER−, PR−), basal-like (ER−, PR−, HER2−, CK5+, and/or HER1+), and unclassified or normal-like (negative for all five markers; ref. 4).

  • P values were calculated to compare the five tumor subgroups, using ANOVA for differences in mean, and χ2 or Fisher exact tests for differences in frequencies.