Distribution (n, %) and MVOR estimates and 95% CIs for several hormone-related and nonhormone-related risk factors and breast cancer characterized by ER+PR+ and ER−PR− subgroups among premenopausal women
Note: the control group is the same for both ERPR subgroup analyses.
| Risk factor . | Controls . | . | ER+PR+ premenopausal cases . | . | . | . | ER−PR− premenopausal cases . | . | . | . | P b . | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| . | n . | (%) . | n . | (%) . | MVORa . | (95% CI) . | n . | (%) . | MVORa . | (95% CI) . | . | |||||||
| Age at menarche (yrs) | ||||||||||||||||||
| ≤11 | 204 | (17) | 122 | (25) | 1.00 | 44 | (17) | 1.00 | 0.04 | |||||||||
| 12 | 336 | (28) | 124 | (25) | 0.59 | (0.39–0.89) | 85 | (32) | 1.08 | (0.62–1.88) | ||||||||
| 13 | 402 | (33) | 137 | (28) | 0.50 | (0.33–0.75) | 83 | (31) | 1.02 | (0.60–1.76) | ||||||||
| ≥14 | 270 | (22) | 112 | (23) | 0.49 | (0.31–0.76) | 55 | (21) | 1.12 | (0.62–2.03) | ||||||||
| Parity | ||||||||||||||||||
| Nulliparousc | 207 | (17) | 82 | (17) | 1.00 | 48 | (18) | 0.32 | ||||||||||
| 1 | 178 | (15) | 75 | (15) | 0.61 | (0.35–1.06) | 48 | (18) | 0.99 | (0.50–1.95) | ||||||||
| 2 | 530 | (43) | 224 | (45) | 0.65 | (0.41–1.04) | 122 | (45) | 1.09 | (0.61–1.95) | ||||||||
| ≥3 | 313 | (26) | 115 | (23) | 0.44 | (0.26–0.75) | 52 | (19) | 0.90 | (0.46–1.76) | ||||||||
| Age at first live birth (yrs) | ||||||||||||||||||
| 13–23 | 382 | (31) | 141 | (29) | 1.00 | 84 | (31) | 1.00 | 0.24 | |||||||||
| 24–27 | 320 | (26) | 130 | (26) | 1.19 | (0.81–1.77) | 61 | (23) | 0.88 | (0.54–1.46) | ||||||||
| ≥28 | 315 | (26) | 141 | (29) | 1.08 | (0.73–1.60) | 77 | (29) | 1.00 | (0.60–1.65) | ||||||||
| Nulliparous | 206 | (17) | 82 | (17) | 1.79 | (1.10–2.91) | 48 | (18) | 0.93 | (0.51–1.68) | ||||||||
| Duration of OCd (yr) | ||||||||||||||||||
| Never or <1 | 329 | (29) | 145 | (33) | 1.00 | 55 | (23) | 1.00 | 0.41 | |||||||||
| ≤4 | 247 | (22) | 91 | (21) | 0.79 | (0.53–1.19) | 50 | (21) | 1.27 | (0.75–2.17) | ||||||||
| 5–9 | 250 | (22) | 93 | (21) | 0.90 | (0.60–1.35) | 54 | (23) | 1.08 | (0.62–1.87) | ||||||||
| ≥10 | 292 | (26) | 110 | (25) | 0.92 | (0.61–1.37) | 81 | (34) | 1.33 | (0.79–2.25) | ||||||||
| BMI (kg/m2)e | ||||||||||||||||||
| ≤25 | 721 | (59) | 295 | (60) | 1.00 | 155 | (59) | 1.00 | 0.03 | |||||||||
| 25.1–27 | 165 | (14) | 68 | (14) | 1.14 | (0.76–1.72) | 38 | (14) | 1.36 | (0.80–2.31) | ||||||||
| >27 | 335 | (27) | 126 | (26) | 0.71 | (0.50–1.00) | 72 | (27) | 1.35 | (0.89–2.05) | ||||||||
| Alcohol (drinks/wk)f | ||||||||||||||||||
| 0 | 309 | (26) | 129 | (27) | 1.00 | 50 | (20) | 1.00 | 0.03 | |||||||||
| ≤1 | 319 | (27) | 122 | (26) | 1.08 | (0.72–1.60) | 75 | (29) | 1.31 | (0.78–2.19) | ||||||||
| 1.5–3 | 324 | (27) | 112 | (23) | 0.84 | (0.55–1.28) | 75 | (29) | 1.36 | (0.81–2.28) | ||||||||
| ≥3.5 | 248 | (21) | 116 | (24) | 1.38 | (0.91–2.10) | 56 | (22) | 0.92 | (0.51–1.68) | ||||||||
| Cigarette smoking (pack-years) | ||||||||||||||||||
| 0 | 651 | (56) | 257 | (54) | 1.00 | 124 | (49) | 1.00 | 0.75 | |||||||||
| 0.1–10 | 241 | (21) | 93 | (20) | 0.91 | (0.62–1.34) | 64 | (25) | 1.05 | (0.66–1.68) | ||||||||
| >10 | 278 | (24) | 124 | (26) | 1.10 | (0.77–1.57) | 66 | (26) | 1.31 | (0.83–2.06) | ||||||||
| Breast feeding (mos) | ||||||||||||||||||
| Never or nulliparous | 557 | (47) | 209 | (44) | 1.00 | 140 | (53) | 1.00 | 0.12 | |||||||||
| 1–6 | 274 | (23) | 112 | (23) | 1.17 | (0.77–1.78) | 56 | (21) | 0.70 | (0.41–1.19) | ||||||||
| >6 | 367 | (31) | 160 | (33) | 1.41 | (0.96–2.08) | 70 | (26) | 0.86 | (0.53–1.39) | ||||||||
| Benign breast disease | ||||||||||||||||||
| No | 998 | (83) | 238 | (53) | 1.00 | 154 | (63) | 1.00 | 0.44 | |||||||||
| Yes | 200 | (17) | 212 | (47) | 3.73 | (2.73–5.09) | 92 | (37) | 3.15 | (2.10–4.72) | ||||||||
| Family history breast cancerg | ||||||||||||||||||
| No | 1102 | (93) | 400 | (84) | 1.00 | 221 | (85) | 1.00 | 0.32 | |||||||||
| Yes | 78 | (7) | 77 | (16) | 1.73 | (1.08–2.76) | 38 | (15) | 2.35 | (1.35–4.10) | ||||||||
| Age group (yrs) | ||||||||||||||||||
| 25–34 | 124 | (10) | 27 | (5) | n/ah | 40 | (15) | n/a | ||||||||||
| 35–39 | 212 | (17) | 64 | (13) | 54 | (20) | ||||||||||||
| 40–44 | 324 | (26) | 129 | (26) | 75 | (28) | ||||||||||||
| 45–49 | 381 | (31) | 177 | (35) | 79 | (29) | ||||||||||||
| 50–64 | 198 | (16) | 103 | (21) | 23 | (9) | ||||||||||||
| Risk factor . | Controls . | . | ER+PR+ premenopausal cases . | . | . | . | ER−PR− premenopausal cases . | . | . | . | P b . | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| . | n . | (%) . | n . | (%) . | MVORa . | (95% CI) . | n . | (%) . | MVORa . | (95% CI) . | . | |||||||
| Age at menarche (yrs) | ||||||||||||||||||
| ≤11 | 204 | (17) | 122 | (25) | 1.00 | 44 | (17) | 1.00 | 0.04 | |||||||||
| 12 | 336 | (28) | 124 | (25) | 0.59 | (0.39–0.89) | 85 | (32) | 1.08 | (0.62–1.88) | ||||||||
| 13 | 402 | (33) | 137 | (28) | 0.50 | (0.33–0.75) | 83 | (31) | 1.02 | (0.60–1.76) | ||||||||
| ≥14 | 270 | (22) | 112 | (23) | 0.49 | (0.31–0.76) | 55 | (21) | 1.12 | (0.62–2.03) | ||||||||
| Parity | ||||||||||||||||||
| Nulliparousc | 207 | (17) | 82 | (17) | 1.00 | 48 | (18) | 0.32 | ||||||||||
| 1 | 178 | (15) | 75 | (15) | 0.61 | (0.35–1.06) | 48 | (18) | 0.99 | (0.50–1.95) | ||||||||
| 2 | 530 | (43) | 224 | (45) | 0.65 | (0.41–1.04) | 122 | (45) | 1.09 | (0.61–1.95) | ||||||||
| ≥3 | 313 | (26) | 115 | (23) | 0.44 | (0.26–0.75) | 52 | (19) | 0.90 | (0.46–1.76) | ||||||||
| Age at first live birth (yrs) | ||||||||||||||||||
| 13–23 | 382 | (31) | 141 | (29) | 1.00 | 84 | (31) | 1.00 | 0.24 | |||||||||
| 24–27 | 320 | (26) | 130 | (26) | 1.19 | (0.81–1.77) | 61 | (23) | 0.88 | (0.54–1.46) | ||||||||
| ≥28 | 315 | (26) | 141 | (29) | 1.08 | (0.73–1.60) | 77 | (29) | 1.00 | (0.60–1.65) | ||||||||
| Nulliparous | 206 | (17) | 82 | (17) | 1.79 | (1.10–2.91) | 48 | (18) | 0.93 | (0.51–1.68) | ||||||||
| Duration of OCd (yr) | ||||||||||||||||||
| Never or <1 | 329 | (29) | 145 | (33) | 1.00 | 55 | (23) | 1.00 | 0.41 | |||||||||
| ≤4 | 247 | (22) | 91 | (21) | 0.79 | (0.53–1.19) | 50 | (21) | 1.27 | (0.75–2.17) | ||||||||
| 5–9 | 250 | (22) | 93 | (21) | 0.90 | (0.60–1.35) | 54 | (23) | 1.08 | (0.62–1.87) | ||||||||
| ≥10 | 292 | (26) | 110 | (25) | 0.92 | (0.61–1.37) | 81 | (34) | 1.33 | (0.79–2.25) | ||||||||
| BMI (kg/m2)e | ||||||||||||||||||
| ≤25 | 721 | (59) | 295 | (60) | 1.00 | 155 | (59) | 1.00 | 0.03 | |||||||||
| 25.1–27 | 165 | (14) | 68 | (14) | 1.14 | (0.76–1.72) | 38 | (14) | 1.36 | (0.80–2.31) | ||||||||
| >27 | 335 | (27) | 126 | (26) | 0.71 | (0.50–1.00) | 72 | (27) | 1.35 | (0.89–2.05) | ||||||||
| Alcohol (drinks/wk)f | ||||||||||||||||||
| 0 | 309 | (26) | 129 | (27) | 1.00 | 50 | (20) | 1.00 | 0.03 | |||||||||
| ≤1 | 319 | (27) | 122 | (26) | 1.08 | (0.72–1.60) | 75 | (29) | 1.31 | (0.78–2.19) | ||||||||
| 1.5–3 | 324 | (27) | 112 | (23) | 0.84 | (0.55–1.28) | 75 | (29) | 1.36 | (0.81–2.28) | ||||||||
| ≥3.5 | 248 | (21) | 116 | (24) | 1.38 | (0.91–2.10) | 56 | (22) | 0.92 | (0.51–1.68) | ||||||||
| Cigarette smoking (pack-years) | ||||||||||||||||||
| 0 | 651 | (56) | 257 | (54) | 1.00 | 124 | (49) | 1.00 | 0.75 | |||||||||
| 0.1–10 | 241 | (21) | 93 | (20) | 0.91 | (0.62–1.34) | 64 | (25) | 1.05 | (0.66–1.68) | ||||||||
| >10 | 278 | (24) | 124 | (26) | 1.10 | (0.77–1.57) | 66 | (26) | 1.31 | (0.83–2.06) | ||||||||
| Breast feeding (mos) | ||||||||||||||||||
| Never or nulliparous | 557 | (47) | 209 | (44) | 1.00 | 140 | (53) | 1.00 | 0.12 | |||||||||
| 1–6 | 274 | (23) | 112 | (23) | 1.17 | (0.77–1.78) | 56 | (21) | 0.70 | (0.41–1.19) | ||||||||
| >6 | 367 | (31) | 160 | (33) | 1.41 | (0.96–2.08) | 70 | (26) | 0.86 | (0.53–1.39) | ||||||||
| Benign breast disease | ||||||||||||||||||
| No | 998 | (83) | 238 | (53) | 1.00 | 154 | (63) | 1.00 | 0.44 | |||||||||
| Yes | 200 | (17) | 212 | (47) | 3.73 | (2.73–5.09) | 92 | (37) | 3.15 | (2.10–4.72) | ||||||||
| Family history breast cancerg | ||||||||||||||||||
| No | 1102 | (93) | 400 | (84) | 1.00 | 221 | (85) | 1.00 | 0.32 | |||||||||
| Yes | 78 | (7) | 77 | (16) | 1.73 | (1.08–2.76) | 38 | (15) | 2.35 | (1.35–4.10) | ||||||||
| Age group (yrs) | ||||||||||||||||||
| 25–34 | 124 | (10) | 27 | (5) | n/ah | 40 | (15) | n/a | ||||||||||
| 35–39 | 212 | (17) | 64 | (13) | 54 | (20) | ||||||||||||
| 40–44 | 324 | (26) | 129 | (26) | 75 | (28) | ||||||||||||
| 45–49 | 381 | (31) | 177 | (35) | 79 | (29) | ||||||||||||
| 50–64 | 198 | (16) | 103 | (21) | 23 | (9) | ||||||||||||
MVOR, model is adjusted for all other variables plus age (continuous) and current strenuous activity.
P (likelihood ratio test) for heterogeneity in MVORs between ER−PR− and ER+PR+; calculated using polytomous logistic regression.
Includes both never pregnant and no live births.
OC, oral contraceptives.
BMI was calculated using “weight 2 years ago” (prediagnosis).
Includes beer, wine and liquor.
First degree relative.
n/a, not available.