Table 3. Subgroup analysis of HR in overall survival (OS).

Analysis	No. of studies	No.of patients	HR(95% CI)	P value	Model	Heterogeneity
						I2 (%)	P
Subgroup1: patient origin
China	11	1062	0.357 (0.286–0.445)	< 0.001	Fixed-effect	0.0%	0.713
Non-China	6	721	0.605 (0.410–0.895)	0.012	Random-effect	79%	< 0.001
Subgroup 2 tumor types
Nervous system	3	1097	0.888 (0.399–1.974)	0.771	Random-effect	92%	< 0.001
Head and neck squamous cell carcinoma	3	571	0.504 (0.177–1.440)	0.206	Random-effect	90%	< 0.001
Respiratory system	6	1051	0.666 (0.557–0.797)	< 0.001	Fixed-effect	25%	0.249
Gastrointestinal system	14	1798	0.674 (0.510–0.892)	0.006	Random-effect	78%	< 0.001
Urinary and reproductive system	6	1995	0.720 (0.505–1.025)	0.068	Random-effect	78%	< 0.001