. 2013 Jun 18;24(8):1605–1614. doi: 10.1007/s10552-013-0237-6

Table 1.

Characteristics of selected cases (women with asynchronous CBC) and controls (women with UBC only) from the WECARE Study population

Variable	Median (range)	Cases (CBC)	Controls (UBC)
Variable	Median (range)	Median (range)	Median (range)
Age at first diagnosis (years)	46 (23–55)	46 (24–55)	46 (23–55)
Age at reference date (years)	51 (27–71)	51 (27–71)	51 (27–69)
Length of at-risk period (years)^a	4 (1–16)	4 (1–16)	4 (1–16)

Variable	Level	Cases (CBC)		Controls (UBC)
Variable	Level	n	%	n	%
Study site	Iowa	107	17	206	17
	Orange and San Diego Counties	105	17	202	17
	Los Angeles	154	24	290	24
	Seattle	94	15	187	15
	Denmark	176	28	339	28
Year of first diagnosis	1985–1988	221	35	422	35
	1989–1992	214	34	414	34
	1993–1996	160	25	309	25
	1997+	41	6	79	6
Chemotherapy	No	355	56	562	46
Chemotherapy	Yes	281	44	662	54
CMF	Yes	155	24	439	36
FAC/FEC	Yes	61	10	119	10
Tamoxifen treatment	No	485	76	861	70
	Yes	139	22	338	28
	Unknown	12	2	25	2
Radiation treatment	Never	322	51	240	20
Radiation treatment	Ever	314	49	984	80
Histology of first breast cancer	Lobular	82	13	120	10
Histology of first breast cancer	Other	554	87	1,104	90
Stage of first breast cancer	Localized	456	72	793	65
Stage of first breast cancer	Regional	180	28	431	35
ER Status of first breast cancer^b	Positive	302	47	656	54
	Negative	165	26	288	24
	Other	169	27	280	23
PR Status of first breast cancer^b	Positive	252	40	536	44
	Negative	144	23	270	22
	Other	240	38	418	34
Menopausal status/age at menopause at first diagnosis	Premenopausal	468	74	919	75
	Postmenopausal age <45	84	13	183	15
	Postmenopausal age ≥45	83	13	118	10
	Unknown	1	0.2	4	0
Family history of breast cancer	None	420	66	954	78
	≥1 First-degree relative	205	32	246	20
	Adopted	11	2	24	2

Includes Caucasian women with SNP call rates ≥95 %, without significant African or Asian ancestry with complete information on tamoxifen treatment and genotype data from both the Omni1-Quad and custom BeadChip platforms (636 CBC cases and 1,224 UBC controls)

CBC = asynchronous contralateral breast cancer; UBC = unilateral breast cancer; CMF = cyclophosphamide, methotrexate, 5-fluorouracil; FAC/FEC = cyclophosphamide, doxorubicin/epirubicin, 5-fluorouracil chemotherapy; ER = estrogen receptor, PR = progesterone receptor

^aBeginning 1 year after first diagnosis extending to the reference date (date of second diagnosis in cases)

^bRefers to receptor status of the first primary breast cancer. The ‘other’ category consists of women for whom no lab test was given, the test was given and the results are unknown or the test was given and the results were borderline