Table 3.

Summarized HRs of overall and subgroup analyses for DFS

Stratified analysis	Study(N)	HR	Z	P	Heterogeneity
					I2	P	Estimated method
DFS	21	1.894(1.456–2.463)	4.76	< 0.001	78.30%	< 0.001	Random-effect
Subgroup analysis for DFS
Publication year
Early year(~ 2007)	6	1.428(0.992–2.055)	1.92	0.055	62.10%	0.022	Random-effect
Later year(2007~ 2016)	15	2.237(1.54–3.249)	4.23	< 0.001	72.00%	< 0.001	Random-effect
Region
Europe	3	1.023(1.005–1.041)	2.51	0.012	53.40%	0.117	Fixed-effect
America	4	1.559(1.155–2.105)	2.9	0.004	8.40%	0.351	Fixed-effect
Asia	14	2.673(2.096–3.409)	7.92	< 0.001	25.60%	0.179	Fixed-effect
Histological type
SCLC
NSCLC	21	1.894(1.456–2.463)	4.76	< 0.001	78.30%	< 0.001	Random-effect
ADC	9	3.186(1.797–5.650)	3.96	< 0.001	62.10%	0.007	Random-effect
SQC	2	1.022(1.004–1.04)	2.42	0.015	0.00%	0.774	Random-effect
Sample size
< 100	7	2.455(1.392–4.330)	3.10	< 0.001	20.30%	0.28	Fixed-effect
> 100	14	1.770(1.340–2.338)	4.02	< 0.001	82.80%	< 0.001	Random-effect
Cutoff value
L(< 20%)	12	2.783(2.141–3.619)	7.64	< 0.001	25.30%	0.196	Fixed-effect
H(≥20%)	6	1.514(1.243–1.844)	4.12	< 0.001	19.40%	0.287	Fixed-effect
Estimated method
Survival curve	2	1.595(1.053–2.416)	2.21	0.027	52.60%	0.146	Fixed-effect
HR(univariate)	6	2.126(1.156–3.909)	2.43	0.015	67.40%	0.009	Random-effect
HR(multivariate)	13	1.892(1.328–2.698	3.53	< 0.001	79.90%	< 0.001	Random-effect