Table 2.

Summarized HRs of overall and subgroup analyses for OS

Stratified analysis	Study(N)	HR	z	P	Heterogeneity
					I2	P	Estimated method
OS	95	1.122(1.089–1.156)	7.56	< 0.001	78.20%	< 0.001	Random-effect
Subgroup analysis
Publication year
Early year(~ 2007)	44	1.307(1.212–1.408)	7.01	< 0.001	72.50%	< 0.001	Random-effect
Later year(2007~ 2016)	51	1.101(1.063–1.142)	5.28	< 0.001	81.20%	< 0.001	Random-effect
Region
Europe	30	1.021(1.001–1.042)	2.05	0.041	71.30%	< 0.001	Random-effect
America	13	1.671(1.266–2.205)	3.63	< 0.001	66.60%	< 0.001	Random-effect
Asia	52	1.821(1.623–2.043)	10.21	< 0.001	78.20%	< 0.001	Random-effect
Histological type
SCLC	4	1.023(1.004–1.042)	3.28	0.001	22.30%	0.277	Fixed-effect
NSCLC	89	1.113(1.081–1.147)	7.11	< 0.001	78.70%	< 0.001	Random-effect
ADC	22	1.219(1.113–1.336)	4.26	< 0.001	76.20%	< 0.001	Random-effect
SQC	9	1.115(0.806–1.542)	0.66	0.512	74.40%	< 0.001	Random-effect
Sample size
< 100	45	1.486(1.340–1.649)	7.71	< 0.001	73.10%	< 0.001	Random-effect
> 100	50	1.083(1.049–1.119)	4.90	< 0.001	81.50%	< 0.001	Random-effect
Cutoff value
L(< 20%)	34	1.962(1.622–2.373)	6.95	< 0.001	74.50%	< 0.001	Random-effect
H(≥20%)	52	1.144(1.094–1.197)	5.91	< 0.001	78.90%	< 0.001	Random-effect
Estimated method
Original data	4	2.043(0.868–4.808)	1.64	0.102	83.90%	< 0.001	Random-effect
Survival curve	23	1.629(1.368–1.940)	5.47	< 0.001	76.30%	< 0.001	Random-effect
HR(univariate)	16	1.511(1.236–1.847)	4.02	< 0.001	56.10%	0.004	Random-effect
HR(multivariate)	53	1.108(1.063–1.155)	4.87	< 0.001	75.30%	< 0.001	Random-effect