Table 1.
Multivariate adjusted* case-control odds ratios and 95% confidence intervals for all breast cancer cases, triple-negative and non triple-negative cases in relation to known and suspected risk factors among women 45 years of age and younger, 1983-1992.
| Triple–negative (ER-/PR-/HER2-) status | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Controls (N=1,569) |
All breast cancer (N=897) | Triple-negative (N=187) | Non triple-negative (N=710) |
||||||||
| n (%) | n (%) | OR | (95% CI) | n (%) | OR | (95% CI) | n (%) | OR | (95% CI) | P Value** | |
| Demographic/Lifestyle factors | |||||||||||
| Age (yrs) | |||||||||||
| <30 | 155 (9.9) | 35 (3.9) | 1.0 | Reference | 9 (4.8) | 1.0 | Reference | 26 (3.7) | 1.0 | Reference | |
| 30-34 | 297 (18.9) | 140 (15.6) | 2.1 | (1.1-3.9) | 38 (20.3) | 2.6 | (0.8-9.1) | 102 (14.4) | 2.0 | (1.0-3.9) | |
| 35-39 | 573 (36.5) | 335 (37.3) | 2.4 | (1.3-4.3) | 79 (42.2) | 2.9 | (0.9-9.8) | 256 (36.1) | 2.2 | (1.2-4.2) | |
| 40-45 | 544 (34.7) | 387 (43.1) | 2.6 | (1.4-4.6) | 61 (32.6) | 2.2 | (0.7-7.4) | 326 (45.9) | 2.7 | (1.4-5.1) | |
| P for trend | .006 | .81 | .002 | .13 | |||||||
| Race§§ | |||||||||||
| White | 1482 (94.6) | 836 (93.7) | 1.0 | Reference | 178 (95.7) | 1.0 | Reference | 658 (93.2) | 1.0 | Reference | |
| Black | 27 (1.7) | 20 (2.2) | 0.9 | (0.4-2.5) | 3 (1.6) | 0.0 | N/A | 17 (2.4) | 1.2 | (0.5-3.2) | |
| Other | 58 (3.7) | 36 (4.0) | 0.9 | (0.5-1.7) | 5 (2.7) | 0.9 | (0.3-3.1) | 31 (4.4) | 0.9 | (0.4-1.8) | .05 |
| Education | |||||||||||
| <College graduate | 1035 (66.0) | 572 (63.8) | 1.0 | Reference | 119 (63.6) | 1.0 | Reference | 453 (63.8) | 1.0 | Reference | |
| College graduate | 533 (34.0) | 325 (36.2) | 1.2 | (1.0-1.6) | 68 (36.4) | 1.3 | (0.9-2.0) | 257 (36.2) | 1.2 | (1.0-1.6) | .61 |
| Annual income‡‡ | |||||||||||
| <15,000 | 184 (11.9) | 81 (9.1) | 1.0 | Reference | 14 (7.5) | 1.0 | Reference | 67 (9.5) | 1.0 | Reference | |
| 15-45/50,000 | 863 (55.9) | 471 (52.9) | 1.3 | (0.8-1.9) | 99 (52.9) | 1.2 | (0.6-2.6) | 372 (52.9) | 1.3 | (0.8-1.9) | |
| 45/50,000+ | 496 (32.1) | 338 (38.0) | 1.3 | (0.8-1.9) | 74 (39.6) | 1.5 | (0.7-3.2) | 264 (37.6) | 1.2 | (0.8-1.9) | |
| P for trend | .39 | .24 | .64 | .55 | |||||||
| Family history of breast cancer | |||||||||||
| None | 807 (67.8) | 363 (50.3) | 1.0 | Reference | 78 (47.6) | 1.0 | Reference | 285 (51.1) | 1.0 | Reference | |
| 1st degree | 95 (8.0) | 150 (20.8) | 3.0 | (2.1-4.1) | 37 (22.6) | 3.5 | (2.1-5.9) | 113 (20.3) | 2.8 | (2.0-4.0) | |
| 2nd degree only | 289 (24.3) | 209 (28.9) | 1.7 | (1.3-2.2) | 49 (29.9) | 1.8 | (1.2-2.8) | 160 (28.7) | 1.7 | (1.3-2.2) | .70 |
| Body mass index (k/m2)† | |||||||||||
| <18.5 | 87 (5.6) | 35 (4.0) | 0.7 | (0.4-1.2) | 6 (3.2) | 0.5 | (0.2-1.7) | 29 (4.2) | 0.8 | (0.4-1.4) | |
| 18.5 – 24.9 | 977 (63.4) | 578 (65.6) | 1.0 | Reference | 121 (65.1) | 1.0 | Reference | 457 (65.8) | 1.0 | Reference | |
| 25.0-29.9 | 269 (17.4) | 151 (17.1) | 1.0 | (0.7-1.3) | 33 (17.7) | 1.1 | (0.6-1.8) | 118 (17.0) | 0.9 | (0.7-1.3) | |
| 30+ | 209 (13.6) | 117 (13.3) | 0.9 | (0.7-1.3) | 26 (14.0) | 1.3 | (0.8-2.2) | 91 (13.1) | 0.8 | (0.6-1.2) | |
| P for trend | .99 | .18 | .54 | .12 | |||||||
| Smoking | |||||||||||
| Never | 801 (51.4) | 464 (52.2) | 1.0 | Reference | 100 (54.6) | 1.0 | Reference | 364 (51.6) | 1.0 | Reference | |
| Former | 332 (21.3) | 189 (21.3) | 0.9 | (0.7-1.2) | 34 (18.6) | 0.8 | (0.5-1.3) | 155 (22.0) | 0.9 | (0.7-1.3) | |
| Current | 424 (27.2) | 236 (26.5) | 0.9 | (0.7-1.2) | 49 (26.8) | 1.0 | (0.6-1.6) | 187 (26.5) | 0.9 | (0.7-1.2) | .29 |
| Alcohol use (drinks/wk) | |||||||||||
| None/<1 | 771 (49.2) | 442 (49.3) | 1.0 | Reference | 88 (47.1) | 1.0 | Reference | 354 (49.9) | 1.0 | Reference | |
| 1-3 | 288 (18.4) | 152 (17.0) | 1.0 | (0.7-1.3) | 29 (15.5) | 0.8 | (0.5-1.4) | 123 (17.3) | 1.0 | (0.7-1.4) | |
| 3+ | 507 (32.4) | 302 (33.7) | 1.1 | (0.9-1.4) | 70 (37.4) | 1.1 | (0.7-1.6) | 232 (32.7) | 1.1 | (0.8-1.4) | |
| P for trend | .54 | .84 | .54 | .49 | |||||||
| Reproductive factors | |||||||||||
| Age at menarche | |||||||||||
| 8-12 | 737 (47.1) | 471 (52.5) | 1.0 | Reference | 98 (52.4) | 1.0 | Reference | 373 (52.5) | 1.0 | Reference | |
| 13-14 | 690 (44.1) | 351 (39.1) | 0.8 | (0.6-1.0) | 77 (41.2) | 0.8 | (0.6-1.2) | 274 (38.6) | 0.7 | (0.6-1.0) | |
| 15+ | 139 (8.9) | 75 (8.4) | 0.8 | (0.5-1.2) | 12 (6.4) | 0.4 | (0.2-1.0) | 63 (8.9) | 0.9 | (0.6-1.4) | |
| P for trend | .03 | .05 | .11 | .33 | |||||||
| Number of live births | |||||||||||
| None | 396 (25.2) | 232 (25.9) | 1.0 | Reference | 53 (28.3) | 1.0 | Reference | 179 (25.2) | 1.0 | Reference | |
| 1-3 | 1057 (67.4) | 621 (69.2) | 0.8 | (0.5-1.3) | 127 (67.9) | 0.9 | (0.4-1.9) | 494 (69.6) | 0.8 | (0.5-1.3) | |
| 4+ | 116 (7.4) | 44 (4.9) | 0.5 | (0.3-1.0) | 7 (3.7) | 0.6 | (0.2-1.9) | 37 (5.2) | 0.5 | (0.3-1.0) | |
| P for trend | .04 | .38 | .04 | .83 | |||||||
| Age at first birth (yrs)‡ | |||||||||||
| None | 390 (24.9) | 230 (25.7) | 1.0 | Reference | 53 (28.3) | 1.0 | Reference | 177 (25.0) | 1.0 | Reference | |
| <20 | 264 (16.8) | 116 (12.9) | 0.6 | (0.3-1.0) | 19 (10.2) | 0.6 | (0.2-1.4) | 97 (13.7) | 0.6 | (0.3-1.0) | |
| 20-29 | 745 (47.5) | 419 (46.8) | 0.8 | (0.5-1.3) | 86 (46.0) | 0.9 | (0.4-2.0) | 333 (47.0) | 0.8 | (0.5-1.3) | |
| 30+ | 170 (10.8) | 131 (14.6) | 1.0 | (0.6-1.8) | 29 (15.5) | 1.2 | (0.5-3.0) | 102 (14.4) | 1.0 | (0.6-1.8) | |
| P for trend§ | .002 | .03 | .009 | .49 | |||||||
| Lactation‖ | |||||||||||
| Never | 313 (26.9) | 189 (28.5) | 1.0 | Reference | 33 (24.6) | 1.0 | Reference | 156 (29.4) | 1.0 | Reference | |
| <12 | 494 (42.5) | 279 (42.0) | 1.1 | (0.8-1.4) | 63 (47.0) | 1.1 | (0.7-1.8) | 216 (40.8) | 1.1 | (0.8-1.5) | |
| 12+ | 356 (30.6) | 196 (29.5) | 1.0 | (0.7-1.4) | 38 (28.4) | 1.0 | (0.6-1.7) | 158 (29.8) | 1.0 | (0.7-1.4) | |
| P for trend | .97 | .99 | .98 | .78 | |||||||
| Abortion | |||||||||||
| Never | 950 (72.9) | 510 (67.3) | 1.0 | Reference | 98 (64.5) | 1.0 | Reference | 412 (68.0) | 1.0 | Reference | |
| Ever | 354 (27.1) | 248 (32.7) | 1.4 | (1.1-1.8) | 54 (35.5) | 1.4 | (0.9-2.2) | 194 (32.0) | 1.4 | (1.1-1.8) | .82 |
| Oral contraceptive use | |||||||||||
| OC use (yrs) | |||||||||||
| Never/<1 | 407 (25.9) | 197 (22.0) | 1.0 | Reference | 22 (11.8) | 1.0 | Reference | 175 (24.7) | 1.0 | Reference | |
| 1+ | 1162 (74.1) | 699 (78.0) | 1.3 | (1.0-1.7) | 165 (88.2) | 2.5 | (1.4-4.3) | 534 (75.3) | 1.2 | (0.9-1.5) | .008 |
| OC duration (yrs)†† | |||||||||||
| 1-<3 | 327 (20.8) | 184 (20.5) | 1.3 | (0.9-1.7) | 35 (18.7) | 1.6 | (0.9-3.3) | 149 (21.0) | 1.2 | (0.9-1.7) | |
| 3-<6 | 357 (22.8) | 220 (24.6) | 1.4 | (1.0-2.0) | 51 (27.3) | 2.8 | (1.5-5.3) | 169 (23.8) | 1.2 | (0.9-1.7) | |
| 6+ | 478 (30.5) | 295 (32.9) | 1.3 | (1.0-1.8) | 79 (42.2) | 2.9 | (1.6-5.3) | 216 (30.5) | 1.1 | (0.8-1.5) | |
| P for trend | .85 | .05 | .45 | .02 | |||||||
| Age at first use (yrs)†† | |||||||||||
| 22+ | 260 (16.6) | 159 (17.7) | 1.2 | (0.9-1.7) | 31 (16.6) | 2.0 | (1.0-4.1) | 128 (18.1) | 1.1 | (0.8-1.6) | |
| 18-<22 | 674 (43.0) | 390 (43.5) | 1.2 | (0.9-1.6) | 92 (49.2) | 2.3 | (1.3-4.1) | 298 (42.0) | 1.1 | (0.8-1.4) | |
| <18 | 228 (14.5) | 150 (16.7) | 1.9 | (1.3-2.7) | 42 (22.5) | 3.7 | (1.9-7.2) | 108 (15.2) | 1.6 | (1.1-2.3) | |
| P for trend | .05 | .13 | .10 | .84 | |||||||
| Years since first use†† | |||||||||||
| 1-<15 | 313 (19.9) | 132 (14.7) | 1.3 | (0.8-1.9) | 36 (19.3) | 2.4 | (1.1-5.1) | 96 (13.5) | 1.1 | (0.7-1.6) | |
| 15-<20 | 462 (29.4) | 277 (30.9) | 1.3 | (1.0-1.8) | 78 (41.7) | 3.0 | (1.6-5.4) | 199 (28.1) | 1.1 | (0.8-1.5) | |
| 20+ | 387 (24.7) | 290 (32.4) | 1.4 | (1.0-1.9) | 51 (27.3) | 2.0 | (1.1-4.0) | 239 (33.7) | 1.3 | (0.9-1.8) | |
| P for trend | .27 | .74 | .25 | .74 | |||||||
| Years since last use†† | |||||||||||
| Current | 120 (7.6) | 43 (4.8) | 1.0 | (0.6-1.8) | 16 (8.6) | 3.1 | (1.2-7.6) | 27 (3.8) | 0.7 | (0.4-1.4) | |
| 1-<5 | 190 (12.1) | 116 (12.9) | 1.9 | (1.3-2.9) | 31 (16.6) | 4.2 | (2.0-8.6) | 85 (12.0) | 1.6 | (1.1-2.5) | |
| 5-<10 | 255 (16.3) | 136 (15.2) | 1.2 | (0.8-1.7) | 41 (21.9) | 3.0 | (1.6-5.9) | 95 (13.4) | 0.9 | (0.6-1.3) | |
| 10-<15 | 339 (21.6) | 213 (23.8) | 1.3 | (1.0-1.8) | 55 (29.4) | 2.6 | (1.4-4.8) | 158 (22.3) | 1.2 | (0.8-1.6) | |
| 15+ | 258 (16.4) | 191 (21.3) | 1.3 | (0.9-1.8) | 22 (11.8) | 1.2 | (0.6-2.6) | 169 (23.8) | 1.3 | (0.9-1.8) | |
| P for trend | .86 | .04 | .39 | .01 | |||||||
*
Risk factors adjusted for age, family history of breast cancer, breastfeeding history and OC duration
†
1 yr prior to reference date
‡
Still and live births
§
P for trend among parous women only
‖
Among parous women
¶
Among gravid women
**
Pheterogeneity (association of risk factor with triple-negative vs. non triple-negative breast cancer)
††
Ptrend and Pheterogeneity among OC users >1 year only
‡‡
Income categories reflect the fact that the two studies combined for the present study used different cut-offs
§§
Due to missing data, race was adjusted for age, breastfeeding history and OC duration, but not family history of breast cancer