Table 1. Risk of breast cancer defined by ER/PR subtype in Australian women under the age of 40 years according to risk factor.
ER+PR+ |
ER+PR− |
ER−PR+ |
ER−PR− |
ER? &/or PR? |
Control | |||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
N=323 | OR (95% CI)c | N=34 | OR (95% CI) | N=80 | OR (95% CI) | N=181 | OR (95% CI) | N=147 | OR (95% CI) | N=564 | LRTb | |
1° relative with breast cancer | ||||||||||||
Yes | 9% | 12% | 8% | 11% | 9% | 4% | ||||||
Yes (ref: No) | 2.5 (1.4–4.6) | 3.4 (1.1–11) | 1.8 (0.6–4.8) | 3.4 (1.8–6.4) | 2.2 (1.1–4.5) | P=0.8 | ||||||
Height | ||||||||||||
⩾163 | 59% | 62% | 70% | 59% | 58% | 55% | P=0.3 | |||||
⩾163 (ref: <163) | 1.2 (0.9–1.6) | 1.3 (0.6–2.7) | 1.8 (1.0–3.1) | 1.3 (0.9–1.8) | 1.4 (0.9–2.1) | |||||||
Body mass index | ||||||||||||
⩾23 | 43% | 50% | 46% | 50% | 51% | 46% | P=0.5 | |||||
⩾23 (ref: <23) | 0.9 (0.7–1.2) | 1.2 (0.6–2.3) | 1.0 (0.6–1.6) | 1.1 (0.8–1.5) | 1.3 (0.9–1.3) | |||||||
Age at menarche | ||||||||||||
⩾13 years | 60% | 65% | 62% | 53% | 60% | 63% | ||||||
⩾13 years (ref: <13) | 0.8 (0.6–1.1) | 0.9 (0.5–1.8) | 0.8 (0.5–1.3) | 0.6 (0.4–0.9) | 0.9 (0.6–1.3) | P=0.5 | ||||||
Ever use of oral contraceptives | ||||||||||||
Yes | 93% | 91% | 96% | 92% | 91% | 91% | ||||||
Yes (ref: No) | 1.1 (0.7–1.9) | 1.3 (0.4–4.0) | 1.1 (0.5–2.5) | 0.9 (0.5–1.6) | 1.0 (0.6–1.9) | P=0.6 | ||||||
Ever had live birth | ||||||||||||
Yes | 69% | 74% | 73% | 72% | 73% | 65% | ||||||
Yes (ref: No) | 1.0 (0.7–1.4) | 1.7 (0.7–4.4) | 1.4 (0.8–2.6) | 1.0 (0.7–1.6) | 1.0 (0.6–1.7) | P=0.9 | ||||||
Age at first live birthd | ||||||||||||
⩾25 | 67% | 64% | 69% | 56% | 56% | 59% | ||||||
⩾25 (ref: <25) | 1.7 (1.1–2.5) | 1.7 (0.7–4.3) | 1.3 (0.7–2.5) | 0.9 (0.6–1.4) | 1.0 (0.6–1.7) | P=0.2 | ||||||
Number of live births | ||||||||||||
1 | 13% | 24% | 28% | 17% | 14% | 12% | ||||||
1 (ref: 0) | 1.1 (0.7–1.7) | 2.6 (0.9–7.1) | 2.6 (1.3–5.2) | 1.3 (0.8–2.3) | 1.1 (0.6–2.1) | |||||||
2 | 35% | 26% | 28% | 36% | 38% | 29% | ||||||
2 (ref: 0) | 1.0 (0.7–1.5) | 1.3 (0.5–3.8) | 1.0 (0.5–2.0) | 1.0 (0.6–1.7) | 1.1 (0.7–1.9) | |||||||
⩾3 | 21% | 24% | 18% | 19% | 21% | 24% | P=0.8 | |||||
⩾3 (ref: 0) | 1.0 (0.5–1.2) | 1.4 (0.5–4.3) | 0.9 (0.4–1.9) | 0.8 (0.4–1.3) | 0.8 (0.4–1.4) |
aPolytomous logistic regression adjusted for study centre, study period, reference age, highest completed education level, country of birth, marital status, affected first-degree relative, height, body mass index, age at menarche, number of live births, and ever used oral contraceptives.
Likelihood ratio test.
Odds ratio with 95% confidence interval.
Parous women only.