Table 1.

Baseline Characteristics and Receipt of Radiation Therapy

	All patients	No RT	%	RT	%	P-value
Entire Cohort	7403	919	12.4	6484	87.6
Demographic Characteristics
Age (years)						<0.001
70 – 74	3869	359	39.1	3510	54.1
75 – 79	3534	560	60.9	2974	45.9
Race						<0.001
White	6766	818	89.0	5948	91.7
Black	301	70	7.6	231	3.6
Other/unknown	336	31	3.4	305	4.7
Comorbidity						<0.001
0	4505	425	46.2	4080	62.9
1	1752	243	26.4	1509	23.3
2 or more	926	160	17.4	766	11.8
Unknown	220	91	9.9	129	2.0
Year of diagnosis						<0.001
1992 – 1995	1611	280	30.5	1331	20.5
1996 – 1999	2432	292	31.8	2140	33.0
2000 – 2002	3360	347	37.8	3013	46.5
Tumor Characteristics
Tumor histology						<0.001
Invasive ductal	5314	609	66.3	4705	72.6
Invasive lobular	597	70	7.6	527	8.1
Other/unknown	1492	240	26.1	1252	19.3
Tumor Grade						<0.001
Low	2385	341	37.1	2044	31.5
Intermediate	3231	345	37.5	2886	44.5
High	989	96	10.4	893	13.8
Unknown	798	137	14.9	661	10.2
Treatment characteristics
Axillary lymph node status						<0.001
Clinical node negative	1954	587	63.9	1367	21.1
Pathologic node negative	5449	332	36.1	5117	78.9
Receipt of chemotherapy						<0.001
No	7034	898	97.7	6136	94.6
Yes	369	21	2.3	348	5.4

Abbreviations: RT (Radiation therapy).

The other/unknown race group includes Asian and Hispanic individuals. These groups have been combined in Table 1 in accordance with SEER-Medicare guidelines to suppress cell sizes < 11. P-value from Pearson’s chi-square test.