Table 3.
Case–case odds ratios and 95% CI for the associations between breast cancer risk factors and subtypes of HR+ tumors defined by levels of tumor proliferation indicated by KI67
| KI67* | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Q1 (comparison group) | Q2 | Q3 | Q4 | ||||||||
| Risk factor | N | N | OR (95% CI) | P‐Value | N | OR (95% CI) | p‐Value | N | OR (95% CI) | p‐Value | p_trend |
| Menarche | |||||||||||
| ≥15 years | 206 | 209 | 1.00 (referent) | 196 | 1.00 (referent) | 201 | 1.00 (referent) | ||||
| 14 years | 236 | 263 | 1.11 (0.85, 1.14) | 0.45 | 244 | 1.07 (0.82, 1.41) | 0.60 | 226 | 0.96 (0.73, 1.26) | 0.76 | 0.49 |
| 13 years | 302 | 253 | 0.85 (0.65, 1.10) | 0.22 | 262 | 0.96 (0.74, 1.25) | 0.75 | 254 | 0.94 (0.72, 1.22) | 0.65 | 0.99 |
| ≤12 years | 450 | 401 | 0.96 (0.75, 1.22) | 0.75 | 384 | 1.01 (0.78, 1.29) | 0.96 | 410 | 1.10 (0.86, 1.41) | 0.44 | 0.30 |
| Parity | |||||||||||
| Parous | 1,119 | 1,011 | 1.00 (referent) | 976 | 1.00 (referent) | 950 | 1.00 (referent) | ||||
| Nulliparous | 158 | 183 | 1.29 (1.03, 1.64) | 0.03 | 175 | 1.30 (1.03, 1.65) | 0.03 | 190 | 1.54 (1.22, 1.95) | <0.0001 | 0.001 |
| BMI | |||||||||||
| <25 kg/m2 | 483 | 477 | 1.00 (referent) | 411 | 1.00 (referent) | 412 | 1.00 (referent) | ||||
| 25–30 kg/m2 | 504 | 418 | 0.79 (0.65, 0.95) | 0.01 | 408 | 0.87 (0.72, 1.05) | 0.16 | 419 | 0.86 (0.72, 1.05) | 0.14 | 0.53 |
| >30 kg/m2 | 256 | 250 | 0.86 (0.69, 1.07) | 0.18 | 288 | 1.05 (0.85, 1.31) | 0.64 | 285 | 0.99 (0.79, 1.24) | 0.93 | 0.67 |
| Combined HT use | |||||||||||
| Never | 151 | 192 | 1.00 (referent) | 269 | 1.00 (referent) | 273 | 1.00 (referent) | ||||
| Former | 37 | 34 | 0.96 (0.57, 1.62) | 0.88 | 35 | 0.81 (0.48, 1.36) | 0.43 | 23 | 0.65 (0.37, 1.16) | 0.14 | 0.12 |
| Current | 72 | 78 | 1.11 (0.74, 1.66) | 0.60 | 56 | 0.66 (0.43, 1.00) | 0.05 | 51 | 0.68 (0.44, 1.05) | 0.09 | 0.03 |
| Family history | |||||||||||
| No | 907 | 923 | 1.00 (referent) | 940 | 1.00 (referent) | 959 | 1.00 (referent) | ||||
| Yes | 266 | 226 | 0.95 (0.76, 1.21) | 0.71 | 182 | 0.89 (0.70, 1.14) | 0.37 | 172 | 0.99 (0.78, 1.27) | 0.98 | 0.97 |
*Quartiles (Q) of KI67 (Q1, <25 percentile (0–1.49%); Q2, 25–50th percentile (1.50–4.29%); Q3, >50–75th percentile (4.30–10.40%); Q4, >75th percentile (>10.40%)) were derived from the distribution of KI67 scores. ORs and corresponding tests are based on data from all cases i.e. both population and non‐population‐based. All models were adjusted for age and study and no evidence was observed of between‐study heterogeneity in study‐specific OR estimates for nulliparity (p‐value = 0.85).
Statistically significant p‐values are indicated in bold.