Table 2.

Baseline characteristics according to contralateral prophylactic mastectomy (CPM) status (N = 107 106) 1998–2003^*

	CPM not performed (n = 98 204)		CPM performed (n = 8902)
Characteristic	No.	%	No.	%	χ2 statistic†
Age, y‡
18–49 (referent)	23 605	24	3731	42	2200
50–59	22 251	23	2629	30
60–90	52 348	53	2542	29
Race and/or ethnicity§
Non-Hispanic white (referent)	72 408	74	7584	85	575.97
Hispanic white	8211	8	469	5
Black	8824	9	414	5
Asian or Pacific Islander	8406	9	407	5
Other unspecified or unknown	355	0	28	0
AJCC 5th cancer stage
0 (referent)	12 833	13	1714	19	382.33
I	31 523	32	3058	34
IIA	24 805	25	2081	23
IIB	18 157	18	1260	14
IIIA	5900	6	468	5
IIIB	4986	5	321	4
Lymph node status
Negative (referent)	51 177	52	4802	54	160.70
1–3 Positive	21 446	22	1863	21
≥4 Positive	15 198	15	1027	12
Unknown	10 383	11	1210	14
Tumor grade
I (referent)	12 879	13	1289	14	122.93
II	36 032	37	3235	36
III	34 601	35	2741	31
IV	4031	4	474	5
Unknown	10 661	11	1163	13
ER status
Positive (referent)	56 043	57	4959	56	43.18
Negative	17 689	18	1460	16
Unknown or not done	24 472	25	2483	28
Histology type
Nonlobular (referent)	79 835	81	6570	74	293.78
Lobular	18 369	19	2332	26
First tumor diagnosis
No (referent)	25 789	26	2882	32	155.64
Yes	72 415	74	6020	68

^*Stage according to the American Joint Committee on Cancer (AJCC) Cancer Staging Manual, 5th edition. ER = estrogen receptor.

^†All P values were less than .001. P values were calculated using the χ² statistic. All statistical tests were two-sided.

^‡Median (interquartile range) age of diagnosis for CPM performed was 52 (45–61) years and for CPM not performed was 61 (50–73) years.

^§Percent data shown represent data analysis down each column; corresponding percent values in the text represent analysis across each row.