Table 1 The baseline characteristics of included studies.

Author, year	Ethnicity	Cancer type	Sample	N^a	Male	Female	Survival	Analysis	mtDNA gene	nDNA gene	NOS score
Bai²⁵	Asian	Breast cancer	Tissue	148	0	148	OS	MV	tRNA-Leu (UUR)	B2M	4
Chang²⁶	Asian	Colorectal cancer	Tissue	194	134	60	DFS	MV	MT-CYB	RNase P gene	9
Chen²⁰	Asian	Glioma	Blood	336	189	147	OS/PFS	MV	MT-ND1	HGB	7
Cui¹⁸	Asian	Colorectal cancer	Tissue	60	30	30	OS	UV	MT-ND1	β-actin	9
Dang²⁷	Asian	Laryngeal cancer	Tissue	204	197	7	OS	MV	MT-ND2	β-actin	9
Feng, 2015	Asian	Cervical cancer	Tissue	122^b	NA	NA	OS	MV	NC_012920 region	B2M	8
He²¹	Asian	HCC	Blood	618	544	74	OS/DFS	MV	MT-ND1	HGB	9
Lee²²	Asian	Gastric cancer	Tissue	109	82	27	OS/DFS	UV	MT-COX1	β-actin	6
Lin²⁸	Asian	Head and neck cancer	Blood	75	75	0	OS	UV	MT-tRNA^leu	18 S	6
Mohideen¹⁷	Caucasian	Colorectal cancer	Blood	273^c	160	116	OS/DFS	MV	MT-ND2	FASLG	8
Osch¹⁶	Caucasian	Colorectal cancer	Tissue	655^c	372	306	OS	UV	D-loop	B2M	8
Qu²⁹	Asian	Colorectal cancer	Blood	598	328	270	OS/DFS	MV/UV	MT-ND1	HGB	8
Tu, 2015	Caucasian	Prostate cancer	Blood	1266	1266	0	PFS	MV	MT-ND1	HGB	7
Wang³⁰	Asian	Colorectal cancer	Tissue	124^c	72	90	OS	UV	MT-ND1	β-actin	7
Weerts³¹	Caucasian	Breast cancer	Tissue	186^b	NA	NA	DMFS	MV	MT-TL1	HMBS	7
Xu³²	Asian	NSCLC	Tissue	128	95	33	OS	MV	NC_012920 region	B2M	8
Yamada³³	Asian	HCC	Tissue	31	27	4	OS	UV	mtDNA	β-actin	8
Yu³⁴	Asian	Breast cancer	Tissue	59	0	59	OS/DFS	UV	D-loop	β-actin	6
Zhang³⁵	Asian	Gastric cancer	Tissue	103	84	19	OS	MV	MT-ND1	β-actin	8
Zhang³⁶	Asian	Glioma	Tissue	124	68	56	OS	MV	MT-ND1	β-actin	8

^aNumber of included patients; ^bUnknown information of gender; ^cexisting missing data.
NOS: Newcastle-Ottawa Quality Assessment Scale; OS: overall survival; DFS: disease-free survival; PFS: progression-free survival; DMFS: distant metastasis-free survival; MV: multivariate analysis; UV: univariate analysis; NSCLC: non-small cell lung cancer; HCC: hepatocellular carcinoma.

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