Table 4.

Univariate and multivariate analysis of the risk factors for brain metastases

Univariate analysis						Multivariate analysis
Variables	Total	BM	%	Chi‐squared value	P‐value	Regression coefficient	SEM	Test statistic	P‐value
Age (y)
≤60	285	93	32.6%	7.102	.008	0.025	0.006	15.188	<.001
>60	267	60	22.5%
Gender
Male	316	75	23.7%	5.853	.016
Female	236	78	33.1%
History of smoking
Yes	210	45	21.4%	6.691	.010
No	342	108	31.6%
Pathological type
Adenocarcinoma	501	145	28.9%	—	.038	—	—	9.366	.009
Squamous cell carcinoma	20	1	5.0%			−3.678	0.411	2.848	.038
Others	31	7	22.6%			0.641	0.276	5.405	.091
Primary site
Left lung	245	71	29.0%	—	.705
Right lung	300	81	27.0%
Mediastinum	4	0	0%
Double lung	3	1	33.3%
Driver gene mutation
EGFR	226	77	34.1%	—	.001	0.456	0.180	6.384	.012
ALK	22	9	40.9%			2.182	0.901	5.870	.015
KRAS	55	12	21.8%
ROS‐1	3	0	0%
BRAF	3	2	66.7%
RET	11	7	63.6%			1.361	0.465	8.557	.003
ERBB2	7	1	14.3%
C‐MET	3	1	33.3%
Double gene mutation	12	4	33.3%
No	210	40	19.0%
EGFR
21 exon	79	28	35.4%	0.324	.851
19 exon	86	30	34.9%
Others	61	19	31.1%
Lymph node metastasis
N0‐1	255	59	23.3%	8.924	.003	−1.031	0.228	20.461	<.001
N2‐3	297	104	35.1%
Imaging features of primary lesions
Central type	202	63	31.2%	—	.366
Peripheral type	347	90	25.9%
Dispersion type	3	1	33.3%
Constant						−6.449	2.322	7.713	.005