Table 3.
Bilateral oophorectomy and risk of breast cancer in BRCA1 and BRCA2 mutation carriers
| Variable | Age-adjusted HR (95% CI) | P | Multivariable* HR (95% CI) | P |
|---|---|---|---|---|
| Oophorectomy† | ||||
| No | 1.00 (Referent) | 1.00 (Referent) | ||
| Yes | 0.91 (0.71 to 1.16) | .43 | 0.89 (0.69 to 1.14) | .35 |
| Family history of breast cancer‡ | ||||
| 0 family members | 1.00 (Referent) | 1.00 (Referent) | ||
| 1 family member | 1.38 (1.06 to 1.76) | .01 | 1.36 (1.06 to 1.75) | .02 |
| ≥2 family members | 1.34 (0.93 to 1.94) | .12 | 1.38 (0.95 to 2.00) | .09 |
| Oral contraceptive use | ||||
| Never | 1.00 (Referent) | 1.00 (Referent) | ||
| Ever | 1.08 (0.87 to 1.35) | .48 | 1.38 (0.95 to 2.00) | .16 |
| BRCA mutation | ||||
| BRCA1§ | 1.00 (Referent) | 1.00 (Referent) | ||
| BRCA2§ | 0.81 (0.62 to 1.08) | .15 | 0.86 (0.62 to 1.20) | .38 |
| Country of residence | ||||
| Poland | 1.00 (Referent) | 1.00 (Referent) | ||
| Canada | 0.78 (0.59 to 1.03) | .08 | 0.77 (0.54 to 1.08) | .13 |
| Other | 1.00 (0.73 to 1.36) | .98 | 0.80 (0.48 to 1.34) | .41 |
| United States | 0.99 (0.74 to 1.34) | .96 | 0.97 (0.69 to 1.38) | .88 |
*
Adjusted for the other variables in the model and also for age at menarche (≤12, 13, ≥14 years), parity (0, 1, 2, 3, ≥4 children), and breastfeeding (ever/never). CI = confidence interval; HR = hazard ratio.
†Oophorectomy was coded as a time-dependent covariate. Oophorectomy refers to bilateral oophorectomies only. Others variables were dichotomized based on exposure at baseline.
‡Number of affected first-degree relatives.
§Women with both a BRCA1 and BRCA2 mutation were coded as missing.