Table 1. Characteristics of eligible studies in the meta-analysis.

Study	Year	Country	Study design	Tumor extenta	Histopathological subtype	Case number	Gender (M/F)	Age (years)	Counting method	Cut-off staining	follow-up (months)	Survival analysis	Quality score*
Rioux-Leclercq	2000	France	Cohort study	all-stage	ccRCC	73	47/26	Mean 64	eyeball	20%	52	CSS	8
Yuba	2001	Japan	Cohort study	all-stage	ccRCC	52	43/9	Mean 58.4	eyeball	5.6%	39	CSS	7
Cheville	2002	USA	Cohort study	localized	ccRCC	232	NA	NA	formal counting	5%	126	CSS	8
Bui	2004	USA	Cohort study	all-stage	ccRCC	224	149/75	Mean 61.5	formal counting	10%	34	CSS	8
Kim	2004	USA	Cohort study	all-stage	ccRCC	318	215/103	Mean 61	eyeball	15%	28	CSS	8
Lehmann	2004	Germany	Cohort study	localized	ccRCC	48	27/21	Median 63	eyeball	6%	91	DFS	6
Dudderidge	2005	UK	Cohort study	localized	ccRCC + non-ccRCC	176	120/56	Mean 63.7	eyeball	12%	44	DFS	8
Kim	2005	USA	Cohort study	metastatic	ccRCC	150	107/43	Mean 59	eyeball	NA	14.8	CSS	6
Pinto	2005	Portugal	Cohort study	all-stage	ccRCC + non-ccRCC	64	34/30	Mean 61.6	eyeball	10%	86	OS	6
Kankuri	2006	Finland	Cohort study	localized	ccRCC + non-ccRCC	37	18/19	Mean 62.2	eyeball	10%	76	OS,DFS	6
Tollefson	2007	USA	Cohort study	all-stage	ccRCC	741	475/266	358/383b (≥65 y/<65 y)	eyeball	≥50 positive cells/mm2	>39.6	CSS	9
Gontero	2008	Italy	Cohort study	all-stage	non-ccRCC	46	37/9	28/18 (≥60 y/<60 y)	eyeball	14%	84.5	OS	8
Parker	2009	USA	Cohort study	all-stage	ccRCC	634	413/221	312/322 (≥65 y/<65 y)	eyeball	≥50 positive cells/mm2	NA	CSS	8
Zubac	2009	Norway	Cohort study	all-stage	ccRCC	172	95/77	Mean 66.6	formal counting	10%	68.4	CSS	8
Kankuri-Tammilehto	2010	Finland	Cohort study	all-stage	ccRCC + non-ccRCC	57	NA	Mean 61	eyeball	10%	>100	OS	6
Weber	2013	Germany	Cohort study	localized	ccRCC	132	80/52	Median 63.5	eyeball	15%	122.4	CSS	8
Gayed	2014	USA	Cohort study	localized	ccRCC	401	239/162	Median 58	eyeball	10%	22	DFS,CSS	8
Teng	2014	China	Cohort study	localized	ccRCC	378	272/106	Mean 53.4	NA	50%	60	DFS	8
Zheng	2014	China	Cohort study	all-stage	ccRCC + non-ccRCC	1239	858/381	53.9	eyeball	15%	56.8	DFS	8
Virman	2016	Findland	Cohort study	all-stage	ccRCC + non-ccRCC	224	132/92	Median 65	formal counting	Median staining	64.8	OS	9

ccRCC: clear cell renal cell carcinoma; OS: overall survival; CSS: cancer-specific survival; DFS: disease-free survival; NA: not available.

^aReported at time of diagnosis.

^b358 patients ≥ 65 years, and other 383 patients < 65 years.

*The quality of the included studies was evaluated using the Newcastle–Ottawa scale.