Table 2.
Relationship between risk factors and breast cancer subtypesa
| Luminal A | Luminal B | HER2‐enriched | Basal‐like | ||||
|---|---|---|---|---|---|---|---|
| n (%) | n (%) | OR (95% CI) | n (%) | OR (95% CI) | n (%) | OR (95% CI) | |
| BMI | |||||||
| <18.5 | 94 (1.9) | 28 (2.2) | 1.31 (0.78‐2.21) | 25 (1.9) | 0.98 (0.56‐1.73) | 14 (2.5) | 1.89 (0.98‐3.64) |
| 18.5‐23.9 | 1969 (40.6) | 582 (45.1) | 1.00 (ref) | 611 (46.1) | 1.00 (ref) | 225 (40.3) | 1.00 (ref) |
| 24.0‐27.9 | 1878 (38.7) | 479 (37.1) | 1.00 (0.85‐1.18) | 489 (36.9) | 0.77 (0.65‐0.91)a | 224 (40.1) | 1.02 (0.81‐1.28) |
| ≥28 | 910 (18.8) | 202 (15.6) | 0.83 (0.67‐1.03) | 199 (15.0) | 0.67 (0.54‐0.83)a | 96 (17.2) | 0.93 (0.69‐1.25) |
| Age of menarche (years) | |||||||
| ≤13 | 1296 (26.7) | 377 (29.3) | 1.16 (0.96‐1.41) | 371 (28.1) | 1.17 (0.96‐1.42) | 163 (29.1) | 1.33 (1.02‐1.74)a |
| 14 | 1072 (22.1) | 275 (21.4) | 1.04 (0.85‐1.27) | 255 (19.3) | 0.99 (0.81‐1.22) | 120 (21.4) | 1.08 (0.82‐1.44) |
| 15 | 779 (16.1) | 202 (15.7) | 1.02 (0.82‐1.26) | 219 (16.6) | 1.12 (0.90‐1.38) | 83 (14.8) | 0.98 (0.72‐1.35) |
| ≥16 | 1701 (35.1) | 432 (33.6) | 1.00 (ref) | 477 (36.1) | 1.00 (ref) | 195 (34.8) | 1.00 (ref) |
| Number of pregnancy | |||||||
| ≤1 | 796 (16.5) | 226 (17.6) | 0.99 (0.68‐1.43) | 226 (17.1) | 1.03 (0.72‐1.48) | 91 (16.3) | 1.13 (0.68‐1.86) |
| 2 | 1368 (28.3) | 386 (30.0) | 1.02 (0.85‐1.22) | 394 (29.8) | 1.04 (0.86‐1.25) | 171 (30.6) | 1.11 (0.86‐1.44) |
| ≥3 | 2665 (55.2) | 674 (52.4) | 1.00 (ref) | 701 (53.1) | 1.00 (ref) | 296 (53.0) | 1.00 (ref) |
| Age at first full‐term pregnancy (years) | |||||||
| <30 | 4166 (89.6) | 1131 (91.7) | 1.00 (ref) | 1158 (90.6) | 1.00 (ref) | 491 (91.3) | 1.00 (ref) |
| ≥30 | 481 (10.4) | 103 (8.3) | 1.15 (0.82‐1.61) | 120 (9.4) | 0.76 (0.53‐1.10) | 47 (8.7) | 1.27 (0.81‐1.98) |
| Number of live births | |||||||
| ≤1 | 3083 (63.9) | 868 (67.6) | 0.89 (0.71‐1.11) | 860 (65.2) | 0.98 (0.78‐1.22) | 345 (61.7) | 0.81 (0.59‐1.11) |
| ≥2 | 1740 (36.1) | 416 (32.4) | 1.00 (ref) | 459 (34.8) | 1.00 (ref) | 214 (38.3) | 1.00 (ref) |
| Months of breast feeding | |||||||
| ≤12 | 1855 (40.7) | 502 (41.4) | 0.98 (0.82‐1.16) | 481 (39.1) | 0.91 (0.77‐1.09) | 200 (38.0) | 0.90 (0.70‐1.15) |
| >12 | 2700 (59.3) | 711 (58.6) | 1.00 (ref) | 749 (60.9) | 1.00 (ref) | 327 (62.0) | 1.00 (ref) |
| Abortion | |||||||
| No | 1353 (28.2) | 350 (27.3) | 1.00 (ref) | 373 (28.4) | 1.00 (ref) | 171 (30.8) | 1.00 (ref) |
| Yes | 3449 (71.8) | 931 (72.7) | 1.00 (0.77‐1.31) | 939 (71.6) | 0.93 (0.72‐1.20) | 385 (69.2) | 0.92 (0.65‐1.30) |
| Oral contraceptive | |||||||
| No | 3956 (85.6) | 1083 (87.1) | 1.00 (ref) | 1101 (85.7) | 1.00 (ref) | 472 (86.3) | 1.00 (ref) |
| Yes | 667 (14.4) | 161 (12.9) | 0.97 (0.78‐1.20) | 183 (14.3) | 0.98 (0.79‐1.20) | 75 (13.7) | 0.94 (0.70‐1.27) |
| HRT | |||||||
| No | 4375 (94.6) | 1188 (95.2) | 1.00 (ref) | 1204 (93.6) | 1.00 (ref) | 522 (95.1) | 1.00 (ref) |
| Yes | 250 (5.4) | 60 (4.8) | 1.00 (0.70‐1.43) | 82 (6.4) | 1.29 (0.94‐1.77) | 27 (4.9) | 0.92 (0.56‐1.52) |
| Menopause | |||||||
| No | 2245 (46.6) | 674 (52.6) | 1.00 (ref) | 490 (37.4) | 1.00 (ref) | 221 (40.0) | 1.00 (ref) |
| Yes | 2572 (53.4) | 608 (47.4) | 1.15 (0.91‐1.45) | 820 (62.6) | 1.94 (1.53‐2.46)a | 332 (60.0) | 1.89 (1.36‐2.62)a |
| Benign breast disease | |||||||
| No | 3056 (64.2) | 763 (60.0) | 1.00 (ref) | 791 (60.6) | 1.00 (ref) | 352 (63.7) | 1.00 (ref) |
| Yes | 1705 (35.8) | 508 (40.0) | 1.09 (0.93‐1.27) | 514 (39.4) | 1.24 (1.06‐1.45)a | 201 (36.3) | 1.05 (0.84‐1.31) |
| Smoking | |||||||
| No | 4268 (89.4) | 1152 (89.9) | 1.00 (ref) | 1179 (89.5) | 1.00 (ref) | 510 (90.9) | 1.00 (ref) |
| Yes | 507 (10.6) | 130 (10.1) | 1.08 (0.85‐1.37) | 138 (10.5) | 0.97 (0.76‐1.23) | 51 (9.1) | 0.77 (0.53‐1.10) |
| Alcohol drinking | |||||||
| No | 4659 (97.9) | 1249 (97.6) | 1.00 (ref) | 1292 (98.3) | 1.00 (ref) | 549 (98.0) | 1.00 (ref) |
| Yes | 101 (2.1) | 31 (2.4) | 1.09 (0.66‐1.79) | 23 (1.7) | 0.73 (0.40‐1.32) | 11 (2.0) | 1.05 (0.50‐2.23) |
| Negative events | |||||||
| No | 3150 (67.6) | 868 (69.1) | 1.00 (ref) | 886 (68.9) | 1.00 (ref) | 368 (67.4) | 1.00 (ref) |
| Yes | 1507 (32.4) | 389 (30.9) | 0.98 (0.83‐1.15) | 400 (31.1) | 0.92 (0.79‐1.08) | 178 (32.6) | 1.00 (0.80‐1.24) |
| First‐degree family history of breast cancer | |||||||
| No | 4540 (93.9) | 1223 (94.7) | 1.00 (ref) | 1240 (94.0) | 1.00 (ref) | 530 (94.8) | 1.00 (ref) |
| Yes | 296 (6.1) | 69 (5.3) | 0.90 (0.65‐1.25) | 79 (6.0) | 0.97 (0.71‐1.33) | 29 (5.2) | 1.02 (0.66‐1.56) |
| Breast density | |||||||
| Non‐dense | 1585 (54.9) | 468 (48.9) | 1.00 (ref) | 578 (50.7) | 1.00 (ref) | 247 (56.4) | 1.00 (ref) |
| Dense | 1304 (45.1) | 490 (51.1) | 0.95 (0.77‐1.18) | 563 (49.3) | 1.42 (1.16‐1.73)a | 191 (43.6) | 0.92 (0.69‐1.23) |
HER2, human epidermal growth factor receptor 2; BMI, body mass index; HRT, hormone replacement therapy.
Odds ratios were adjusted for age, marriage, education, average monthly income, current occupations, age at first marriage, and all above risk factors for breast cancer.
a
Statistically significant at P < 0.05.