Table 3. Results of the meta-analysis 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	32	4854	0.874 (0.711-1.073)	0.197	72.8%	<0.001
	Ethnicity
	Asian	14	2074	0.792 (0.537-1.168)	0.240	78%	<0.001
	Caucasian	18	2780	0.91 (0.716-1.158)	0.444	68.2%	<0.001
	Tumor location
	OSCC	10	1198	0.726 (0.470-1.121)	0.148	84.7%	<0.001
	NPC	7	795	0.692 (0.523-0.915)	0.01	0.0%	0.855
	OPSCC	3	495	0.975 (0.771-1.234)	0.835	0.0%	0.403
	HPSCC	1	83	1.300 (0.700-2.415)	0.407	-	-
	SSCC	1	53	1.355 (0.739-2.485)	0.326	-	-
	LSCC	1	260	0.635 (0.393-1.025)	0.063	-	-
	Sample size
	Large	12	3132	1.022 (0.790-1.321)	0.87	71.4%	<0.001
	Small	20	1722	0.77 (0.575-1.031)	0.08	66.6%	<0.001
DFS	Overall	13	2011	0.874 (0.523-1.465)	0.607	93.9%	<0.001
	Ethnicity
	Asian	5	617	0.824 (0.290-2.338)	0.716	94.2%	<0.001
	Caucasian	8	1394	0.883 (0.638-1.221)	0.451	62.4%	0.009
	Tumor location
	OSCC	3	247	0.610 (0.208-1.793)	0.369	70.5%	0.034
	NPC	4	549	1.042 (0.349-3.111)	0.941	94.9%	<0.001
	SSCC	1	53	1.834 (0.955-3.522)	0.068	-	-
	OPSCC	1	181	1.090 (0.783-1.518)	0.610	-	-
	LSCC	1	260	0.591 (0.350-0.997)	0.048	-	-
	Sample size
	Large	4	1167	0.829 (0.597-1.151)	0.263	57.5%	0.07
	Small	9	844	0.900 (0.454-1.785)	0.762	91.7%	<0.001
PFS	Overall	7	630	0.996 (0.632-1.569)	0.986	62.1%	0.015
	Ethnicity
	Asian	4	318	0.879 (0.585-1.321)	0.534	24.2%	0.266
	Caucasian	3	312	1.219 (0.372-3.997)	0.744	82.6%	0.003
	Tumor location
	OSCC	2	169	0.706 (0.416-1.197)	0.196	7.8%	0.298
	HPSCC	1	83	1.350 (0.737-2.473)	0.331	-	-
	NPC	2	227	0.762 (0.503-1.154)	0.200	0.0%	0.935
	Sample size
	Large	1	161	0.770 (0.476-1.246)	0.287	-	<0.001
	Small	6	469	1.058 (0.600-1.876)	0.845	66.2%	0.011
DSS	Overall	5	699	0.779 (0.330-1.839)	0.569	84.7%	<0.001
DMFS	Overall	3	361	0.599 (0.346-1.035)	0.066	0.0%	0.604