Table 4 Standardised incidence ratios (SIRs) of breast cancer by the number of first-degree relatives diagnosed with breast cancer of ⩽50 years
Observed (rate per 105) | Expected (rate per 105) | SIRs | 95% CI | P -value | |
|---|---|---|---|---|---|
No first-degree relative with breast cancer of ⩽50 years (N=607) | 25 (678.2) | 7.11 (192.9) | 3.52 | 2.38–5.19 | <0.0001 |
One first-degree relative with breast cancer of ⩽50 years (N=677) | 27 (646.9) | 6.29 (150.7) | 4.29 | 2.95–6.25 | <0.0001 |
Two or more first-degree relatives with breast cancer of ⩽50 years (N=207) | 12 (965.4) | 3.08 (247.8) | 3.90 | 2.23–6.81 | 0.0006 |
