Table 2. Risk of breast cancer for mothers and sisters of index cases.

	Observed	Expected	SIR (95% CI)
Mothers and sisters combined	59	11.83	4.99 (3.86–6.44)
Mothers	48	10.41	4.61 (3.48–6.12)
Sisters	11	1.42	7.73 (4.28–14.00)
San Francisco	15	3.15	4.77 (2.88–7.91)
Ontario	17	2.86	5.95 (3.70–9.58)
Melbourne and Sydney	27	5.83	4.63 (3.18–6.75)
Mothers and sisters of BRCA1-positive index cases	8	0.61	13.13 (6.57–26.26)
Mothers and sisters of BRCA2-positive index cases	5	0.40	12.52 (5.21–30.07)
Mothers and sisters of BRCA1- and BRCA2-negative index cases	36	8.92	4.03 (2.91–5.93)
Mothers and sisters of BRCA1 and BRCA2 untested index cases	10	1.91	5.23 (2.81–9.72)
Mothers of BRCA1- and BRCA2-negative index cases	30	7.77	3.86 (2.70–5.23)
Sisters of BRCA1- and BRCA2-negative index cases	6	1.16	5.19 (2.33–11.54)

Abbreviations: CI=confidence interval; SIR=standardised incidence ratio.