Table 1. The main information of included studies in the meta-analysis.

Study	Year	Cancer type	Total number	Tumor stage	Follow-up	Therapy	Detection	Clinical	Analysis	NOS
				I–II/III–IV	(months)		method	outcomes
Zhang et al. [24]	2014	NSCLC	192	129/63	> 60	NA	qRT-PCR	OS,	M	6
Iliev et al. [29]	2016	Bladder cancer	47	NA	42 ± 5	Surgery	qRT-PCR	OS	U	7
Jiang et al. [26]	2016	ESCC	218	96/114	17 (12–72)	Chemotherapy	qRT-PCR	OS	M	7
Lin et al. [32]	2016	NSCLC	89	69/20	> 80	NA	qRT-PCR	OS	U	6
Ma et al. [28]	2016	Osteosarcoma	76	64/12	44 (3–60)	Surgery	qRT-PCR	OS,PFS	M	7
Niu et al. [33]	2017	SCLC	33	16/17	NA	NA	qRT-PCR	OS	U	7
Sun et al. [25]	2016	Colorectal cancer	120	NA	36 (2–60)	Surgery	qRT-PCR	OS	U	7
Wang et al. [30]	2017	CCRCC	203	119/84	> 70	Surgery	qRT-PCR	OS	M	6
Zhang et al. [18]	2016	Gastric cancer	100	57/43	> 60	Surgery	qRT-PCR	OS	M	7

OS = overall survival; NSCLC = non-small cell lung cancer; ESCC = esophageal squamous cell carcinoma; SCLC = small cell lung cancer; CCRCC = clear cell renal cell carcinoma; NA = not available; Multivariate: multivariate analysis; Univariate: univariate analysis; PFS = progression free survival; NOS = Newcastle-Ottawa Scale.