Table 1.

Clinicopathological features of the included patients

	Study population
	Training		Validation		P a
	N	%	N	%
Year of diagnosis
2010	851	23.60	870	24.21	NS
2011	962	26.68	991	27.58
2012	854	23.68	884	24.60
2013	939	26.04	848	23.60
County type
Metropolitan	2991	82.95	2950	82.10	NS
Nonmetropolitan/unknown	615	17.05	643	17.90
Race
White	2839	78.73	2858	79.54	NS
African American	614	17.03	593	16.50
Others	153	4.24	142	3.95
Age group
<=60	2046	56.74	1987	55.30	NS
>60	1560	43.26	1606	44.70
Laterality
Left	1798	49.86	1803	50.18	NS
Right	1778	49.31	1749	48.68
Othersb	30	0.83	41	1.14
Primary site
Nipple/central portion	219	6.07	243	6.76	NS
UIQ	274	7.60	243	6.76
LIQ	147	4.08	146	4.06
UOQ	979	27.15	1001	27.86
LOQ	243	6.74	217	6.04
Overlapping/unknown	1744	48.36	1743	48.51
Charlson/Deyo score
0	2950	81.81	2923	81.35	NS
1	530	14.70	516	14.36
2	126	3.49	154	4.29
Histology
IDC	2751	76.29	2715	75.56	NS
ILC	346	9.60	336	9.35
NOS/others	509	14.12	542	15.08
T‐stage
T0–T1	491	13.62	479	13.33	NS
T2	856	23.74	875	24.35
T3	418	11.59	387	10.77
T4	522	14.48	528	14.70
Tx	1319	36.58	1324	36.85
N‐stage
N0	372	10.32	399	11.10	NS
N1	712	19.74	714	19.87
N2	522	14.48	532	14.81
N3	514	14.25	459	12.77
Nx	1486	41.21	1489	41.44
Grade
I	257	7.13	244	6.79	NS
II	1441	39.96	1459	40.61
III	1908	52.91	1890	52.60
ER
Negative	972	26.96	942	26.22	NS
Positive	2634	73.04	2651	73.78
PR
Negative	1449	40.18	1384	38.52	NS
Positive	2157	59.82	2209	61.48
Her‐2
Negative	2668	73.99	2663	74.12	NS
Positive	938	26.01	930	25.88
Bone metastasis
No	1351	37.47	1332	37.07	NS
Yes	2255	62.53	2261	62.93
Lung metastasis
No	2672	74.10	2651	73.78	NS
Yes	934	25.90	942	26.22
Liver metastasis
No	2701	74.90	2736	76.15	NS
Yes	905	25.10	857	23.85
Brain metastasis
No	3382	93.79	3388	94.29	NS
Yes	224	6.21	205	5.71
Breast surgery
No_surgery	1401	38.85	1427	39.72	NS
Bcs	616	17.08	620	17.26
Mastectomy	1589	44.07	1546	43.03
Radiation therapy
No	2123	58.87	2132	59.34	NS
Yes	1483	41.13	1461	40.66
Chemotherapy
None	1360	37.71	1358	37.80	NS
Single‐agent chemotherapy	492	13.64	504	14.03
Multiagent chemotherapy	1754	48.64	1731	48.18

ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor 2; LIQ, lower‐inner quadrant; LOQ, lower‐outer quadrant; UIQ, upper‐inner quadrant; UOQ, upper‐outer quadrant; BCS, breast‐conserving surgery; IDC, infiltrating ductal carcinoma; ILC, infiltrating lobular carcinoma; NOS, non otherwise specific.

^aChi‐square test.

^bBilateral/side unspecified/unknown included.