Table 4. Sensitivity analysis results for high-quality studies on the prognostic effects of PD-L1 in HNC patients.

	Variable	Study no.		Sample size	HR (95% CI)	P value		Heterogeneity
								I2	P value
OS	Overall	17		2581	0.754 (0.568-1.002)	0.051		76.6%	<0.001
	Ethnicity
	Asian	7		1255	0.720 (0.385-1.348)	0.305		88.1%	<0.001
	Caucasian	10		1326	0.742 (0.578-0.954)	0.020		46.1%	0.054
	Tumor location
	OSCC	5		531	0.653 (0.292-1.462)	0.300		90.7%	<0.001
	NPC	3		389	0.649 (0.458-0.920)	0.015		0.0%	0.744
	OPSCC	3		495	0.975 (0.771-1.234)	0.835		0.0%	0.403
	LSCC	1		260	0.635 (0.393-1.025)	0.063		-	-
	Sample size
	Large	7		1715	0.984 (0.659-1.468)	0.936		79.5%	<0.001
	Small	10		866	0.582 (0.426-0.796)	0.001		50.3%	0.034
DFS	Overall	7		1066	0.928 (0.618-1.392)	0.717		69.4%	0.003
	Ethnicity
	Asian	3		416	0.809 (0.241-2.720)	0.732		85.8%	0.001
	Caucasian	4		650	0.938 (0.663-1.328)	0.719		43.6%	0.150
	Tumor location
	OSCC		2	148	0.699 (0.114-4.263)		0.697	78.4%	0.032
	NPC		2	348	1.215 (0.288-5.133)		0.791	91.0%	0.001
	OPSCC		1	181	1.090 (0.783-1.518)		0.610	-	-
	LSCC		1	260	0.591 (0.351-0.996)		0.048	-	-
	Sample size
	Large	3		650	0.753 (0.485-1.171)	0.208		66.8%	0.049
	Small	4		416	1.146 (0.536-2.450)	0.725		71.0%	0.016
PFS	Overall	3		188	0.618 (0.388-0.985)	0.043		0.0%	0.867