Table 1. Distribution patterns of characteristics among cases with and without tissue and data for ER/PR/HER-2 status, CASH study.

Factor	Cases excluded from analysis (n = 2,627)		Cases in analysis (n = 890)		p-Value
	N	%	N	%
Agea
<35	266	10.1	85	9.6
35–39	342	13.0	110	12.4
40–44	467	17.8	159	17.9
45–49	676	25.7	204	22.9
50–54	763	29.0	294	33.0
55+	113	4.3	38	4.3	N/C
Missing	0		0
Racea
White	2,233	85.0	810	91.0
Black	296	11.3	48	5.4
Other	98	3.7	32	3.6	N/C
Missing	0		0
Age at menarche
<12	651	33.6	214	35.7
12	664	36.9	241	34.6
13	729	29.1	234	29.4
14+	575	0.4	199	0.3	0.67
Missing	8		2
Parity
0	447	17.2	129	14.5
1	334	12.8	95	10.7
2	685	26.3	268	30.2
3	563	21.6	191	21.5
4+	577	22.1	204	23.0	0.059
Missing	21		3
Age at first birth (among parous)
<20	439	20.7	148	19.8
20–22	626	29.6	219	29.2
23–24	377	17.8	147	19.6
25+	675	31.9	235	31.4	0.72
Missing	510		141
Months of breastfeeding (among parous)
0	1,158	54.1	410	54.4
1–5	526	24.6	211	28.0
6+	457	21.3	132	17.5	0.037
Missing	486		137
Infertility problems
No	2,018	81.3	690	81.2
Yes	465	18.7	160	18.8	0.95
Missing	144		40
Duration (months) of OC useb
0	1,167	44.6	409	46.2
1–5	131	5.0	36	4.1
6–11	562	21.5	176	19.9
12–60	544	20.8	193	21.8
>60	212	8.1	72	8.1	0.61
Missing	11		4
Menopausal status (abbreviated)
Premenopausal	1,184	46.5	392	45.9
Perimenopausal	494	19.4	153	17.9
Postmenopausal	867	34.1	309	36.2	0.44
Missing	82		36
Benign breast disease
No	2,137	90.2	736	92.9
Yes	442	9.8	143	7.1	0.55
Missing	48		11
Family history of breast cancer
No	2,168	87.6	720	87.7
Yes	307	12.4	101	12.3	0.94
Missing	152		69
BMI (kg/m2) at reference (WHO categories)
≤18.5	114	4.4	33	3.7
18.6–25.0	1,863	71.3	615	69.4
25.1–30.0	460	17.6	174	19.6
>30.0	175	6.7	64	7.2	0.43
Missing	15		4
Breast cancer tumor stage
0			22	2.5
I			396	44.5
II			430	48.3
III			0	0.0
IV			31	3.5
Missing			11	1.2
Breast cancer tumor histology
Ductal carcinoma in situ			32	3.6
Invasive ductal carcinoma			642	72.1
Lobular carcinoma in situ			51	5.7
Invasive lobular carcinoma			1	0.1
Medullary carcinoma			59	6.6
Other			100	11.2
Missing			5	0.6

^aMatching factors thus p-values were not calculated (N/C)

^bIncluded women who are currently pregnant, recently pregnant, or currently breast feeding