Table 1.

Baseline characteristics of BC brain metastases (BCBM) patients included from SEER data cohort

Characteristic		Cases	%
Age at diagnosis	< 40	141	7.29
	40–49	251	12.98
	50–59	529	27.37
	60–69	576	29.80
	70–79	307	15.88
	80 +	129	6.67
Months from diagnosis to therapy	0 month	877	45.37
	≥ 1 month	739	38.23
	Unknown	317	16.40
Subtype	HR + /HER2−	717	37.09
	HR + /HER2 +	308	15.93
	HR−/HER2 +	239	12.36
	HR−/HER2−	333	17.23
	Unknown	336	17.38
Race	White	1447	74.86
	Black	307	15.88
	Other	179	9.26
Histological type	IDC	1259	65.13
	ILC	97	5.02
	Mixed	70	3.62
	Other	507	26.23
Marital status	Married	790	40.87
	Singled	495	25.61
	Widow/divorced/other	648	33.52
T Stage	T1	196	10.14
	T2	412	21.31
	T3	248	12.83
	T4	640	33.11
	Unknown	437	22.61
N Stage	N0	378	19.56
	N1	802	41.49
	N2	171	8.85
	N3	280	14.49
	Unknown	302	15.62
Grade	Well differentiated	67	3.47
	Moderate differentiated	448	23.18
	Poorly differentiated	756	39.11
	Unknown	662	34.25
Median household income(inflation adjusted)	< 40,000$	104	5.38
	40,000–49,999$	219	11.33
	50,000–59,999$	292	15.11
	60,000–69,999$	642	33.21
	70,000$ +	676	34.97
Chemotherapy	No/unknown	878	45.42
	Yes	1055	54.58
Radiotherapy	No/unknown	757	39.16
	Yes	1176	60.84
Surgery	No/unknown	1699	87.89
	Yes	234	12.11
Bone metastases	No/unknown	680	35.18
	Yes	1253	64.82
Liver metastases	No/unknown	1289	66.68
	Yes	644	33.32
Lung metastases	No/unknown	1092	56.49
	Yes	841	43.51
Distant lymph nodes metastases	No/unknown	1649	85.31
	Yes	284	14.69
Distant other metastases	No/unknown	1720	88.98
	Yes	213	11.02