Table 1.

Family histories* of all women under study (N = 1,987), of all women with breast cancer (n = 136) and of all women with breast cancer under the age of 50 (n = 73)

Presence of Family characteristics	All women	Women with breast cancer
		Breast cancer at any age	Log rank; P	Breast cancer under age 50	Log rank; P
	N (%)	N (%)		N (%)
Total	1987 (100)	136 (6.8)		73 (3.7)
≥ 2 cases of female breast cancer in first or second-degree relatives	614 (30.9)	54 (39.7)	7.39; P = .007	31 (5.0)	5.02; P = .03
≥ 2 cases of female breast cancer in first-degree relatives	165 (8.3)	20 (14.7)	5.23; P = .02	13 (17.8)	9.85; P = .002
≥ 1 case of female breast cancer under age 50	789 (39.7)	52 (6.6)	12.47; P = .0004	35 (4.4)	7.85; P = .005
≥ 2 cases of female breast cancer under age 50	113 (5.7)	10 (8.8)	1.92; P = .17	10 (8.8)	12.33; P = .0004
≥ 1 case of female breast cancer under age 40	231 (11.6)	18 (7.8)	12.01; P = .0005	12 (5.2)	8.52; P = .004
≥ 2 cases of female breast cancer under age 40	10 (0.5)	-	-	-	-
≥ 1 case of female breast cancer under age 30	33 (1.7)	1 (3.0)	-	1 (3.0)	-
Male breast cancer	12 (0.6)	1 (8.0)	-	1 (8.0)	-
Bilateral breast cancer in affected sister (index patient)	104 (5.2)	16 (15.4)	13.94; P = .0002	11 (10.6%)	15.00; P = .0001
Ovarian cancer	54 (2.7)	5 (9.3)	1.93; P = .16	3 (5.5%)	1.23; P = .27
Breast and ovarian cancer in one person	8 (0.4)	2 (25.0)	12.05; P = .0005	2 (25%)	14.00; P = .0002
Prostate cancer under age 60	43 (2.1)	1 (2.3)		1 (2.3%)
DCIS in affected sister (index patient)	169 (8.5)	15 (8.9)	0.97; P = .32	7 (4.1%)	0.04; P = .84

* To avoid dependency between women in families with more than one sister, sisters other than the index patient were excluded from the family history of the women under study.