Table 2.

Baseline characteristics among estrogen and progesterone receptor negative, HER2-positive subgroups stratified by trastuzumab treatment.

Characteristic N (%)	ER/PR(−)* / HER2+* Without trastuzumab N = 257	ER/PR(−) / HER2+ With trastuzumab N = 292	P-value
Median age (years)	49	51	0.336
Menopausal status
Pre	113 (44)	122 (42)	0.307
Post	110 (43)	143 (49)
Unknown	34 (13)	27 (9)
T-stage
T1	102 (40)	85 (29)	0.010
T2	102 (40)	112 (39)
T3	19 (7)	30 (10)
T4	33 (12)	62 (21)
Unknown	1 (1)	3 (1)
N-stage
N0	121 (47)	116 (40)	0.004
N1	95 (37)	103 (35)
N2	18 (7)	16 (5)
N3	21 (8)	55 (19)
Unknown	2 (1)	2 (1)
Stage Group
I	70 (27)	52 (18)	0.010
II	114 (44)	129 (44)
III	71 (28)	108 (37)
Unknown	2 (1)	3 (1)
Nuclear grade
1	0 (0)	0 (0)	0.837
2	23 (9)	25 (9)
3	223 (87)	258 (88)
Unknown	11 (4)	9 (3)
LVSI†
Negative	154 (60)	180 (62)	0.680
Positive	94 (37)	102 (35)
Unknown	9 (3)	10 (3)
Surgery/Radiation
BCT‡ + RT‡	88 (34)	88 (30)	0.081
Mastectomy + RT	90 (35)	125 (43)
Mastectomy no RT	73 (29)	64 (22)
Unknown	6 (2)	15 (5)
Surgical Margins
Negative	222 (86)	260 (89)	0.278
Positive/close	23 (9)	19 (7)
Unknown	12 (5)	13 (4)
Chemotherapy
Neoadjuvant only	80 (31)	71 (24)	<0.001
Adjuvant only	148 (58)	112 (39)
Both	29 (11)	109 (37)
Chemotherapy Agents
Anthracycline-based	59 (23)	10 (3)	<0.001
Taxane-based	2 (1)	38 (13)
Antracycline + Taxane	192 (74)	240 (82)
Other/Unknown	4 (2)	4 (2)
Era of Treatment
Before 2004	213 (83)	59 (20)	<0.001
2004 and after	44 (17)	233 (80)

^*ER/PR(−) = Estrogen and Progesterone Receptor Negative; HER2+ = Human epidermal growth factor receptor 2 positive

^†LVSI = Lymphovascular space invasion

^‡BCT = Breast conservation therapy; RT = Radiation therapy