Table 1.

Clinicopathologic and Treatment Characteristics

Characteristic	Variable	No PMRT (N=924) N (%)	PMRT (N=163) N (%)	p-value
Age	<40	147 (16%)	33 (20%)	0.019
	40–50	264 (29%)	62 (38%)
	50–60	232 (25%)	36 (22%)
	60–70	150 (16%)	17 (10%)
	>70	131 (14%)	15 (9%)
Tumor Size	0.1–2.0 cm	561 (61%)	77 (47%)	0.0013
	2.1–5.0 cm	363 (39%)	86 (53%)
Histological Grade*	I	20 (2%)	2 (1%)	0.029
	II	204 (22%)	23 (14%)
	III	572 (62%)	118 (72%)
Nuclear Grade*	I	20 (2%)	0 (0%)	0.044
	II	366 (40%)	57 (35%)
	III	365 (40%)	77 (47%)
Extensive Intraductal Component*	Yes	243 (26%)	41 (25%)	0.74
	No	678 (73%)	122 (75%)
Multifocal/Multicentric	Yes	390 (42%)	74 (45%)	0.45
	No	534 (58%)	89 (55%)
Lymphovascular Invasion	Yes	408 (44%)	104 (64%)	<.0001
	No	516 (56%)	59 (36%)
Extracapsular Extension	Yes	115 (12%)	54 (33%)	<.0001
	No	809 (88%)	108 (66%)
Axillary Procedure	SLNB only	60 (6%)	3 (2%)	0.0191
	ALND	864 (94%)	160 (98%)
Number of Positive Nodes	1	577 (62%)	51 (31%)	<.0001
	2	242 (26%)	61 (37%)
	3	105 (11%)	51 (31%)
Size of Axillary Nodal Metastasis*	Macroscopic	661 (72%)	143 (88%)	<.0001
	Microscopic	259 (28%)	19 (12%)
Estrogen Receptor*	Positive	710 (77%)	117 (72%)	0.12
	Negative	197 (21%)	44 (27%)
Progesterone Receptor*	Positive	552 (60%)	99 (61%)	0.84
	Negative	358 (39%)	62 (38%)
HER2 Status*	Amplified	107 (12%)	24 (15%)	0.61
	Not Amplified	611 (66%)	121 (74%)
Systemic Chemotherapy*	Yes	793 (86%)	157 (96%)	0.0002
	No	129 (14%)	6 (4%)

^*Percentages are out of total sample size for each group (includes unknowns)

PMRT, postmastectomy radiation therapy; SLNB, sentinel lymph node biopsy; ALND; axillary lymph node dissection