Family history and relative risks of breast and ovarian stratified according to the location of the BRCA1 mutation
| Mutations located 5′ of OCCR | Mutations located within OCCR | Mutations located 3′ of OCCR | Overall | p Value | |
|---|---|---|---|---|---|
| BRCA1 | |||||
| Families n (%) | 181 (31) | 137 (24) | 264 (45) | 582 | |
| Ratio breast cancer to ovarian cancer cases* | 3.8 | 2.6 | 4.5 | 3.7 | <0.001 |
| Mean number of breast cancer cases/family | 3.7 | 3.3 | 4.2 | 3.8 | 0.011† |
| Mean number of ovarian cancer cases/family | 1.0 | 1.3 | 0.9 | 1.1 | 0.006† |
| Mean number of females/family | 26.4 | 23.9 | 28.8 | 26.9 | 0.091† |
| RR‡ breast cancer (95% CI) | 1.10 (0.94 to 1.28) | 1 (Ref) | 1.26 (1.09 to 1.45) | <0.001§ | |
| RR‡ ovarian cancer (95% CI) | 0.68 (0.53 to 0.87) | 1 (Ref) | 0.63 (0.50 to 0.79) | ||
BRCA1 Ovarian Cancer Cluster Region (OCCR) between nucleotide (nt) 2401 and 4190; Ref= mutations located in OCCR as reference group; RR, relative risk.
*13 BRCA1 mutation carriers diagnosed with both breast and ovarian cancer were excluded from this analysis.
†Test: Equality of populations (Kruskal–Wallis test).
‡=Risks associated with 5′ (below nt 2401) and 3′ (above nt 4190) were estimated relative to mutations in the OCCR using an extended MENDEL model without ascertainment correction.
§p Value from comparing the extended model with the baseline model.