Table 1.

The characteristics of the included studies.

Study ID	Country	Gender (male/female)	Metformin usage	Age (mean, years)	Sample size	Tumor size (≤5 cm/>5 cm)	Child–Pugh grading (A/B/C/D)	BCLC (0/A/B/C/D)	Curative therapy for HCC
Chen et al., (14)	China	21/32	Metformin, 750 mg/day	64.2–67.4	21	10/11	10.2 ± 4.5	NR	Radiofrequency ablation
			Sulfonylurea + insulin		32	13/19	9.7 ± 3.4	NR	Radiofrequency ablation
Jang et al., (13)	South Korea	57/19	Metformin, 1,000 mg/day	NR	19	13/6	A: 18, B: 1	A: 12, B: 7	Stereotactic body radiotherapy
			Sulfonylurea + thiazolidinedione + others, dose NR		57	37/20	A: 37, B: 20	A: 36, B: 21	Stereotactic body radiotherapy
Seo et al., (12)	South Korea	598/153	Metformin + sulfonylurea + thiazolidinedione, dose NR	60	533	NR	NR	NR	Hepatic resection
			Sulfonylurea + thiazolidinedione, dose NR		218	NR	NR	NR	Hepatic resection
Chan et al., 2016 (16)	China	3,346/1,264	Metformin, dose NR	64	1,632	NR	NR	NR	Hepatic resection
			Other antidiabetic drugs		2,978	NR	NR	NR	Hepatic resection
Kang et al., (15)	South Korea	214/56	Metformin, dose NR	60.8	45	45/0	A:45	NR	Hepatic resection
			Other antidiabetic drugs		225	225/0	A:225	NR	Hepatic resection
Luo et al., (17)	China	163/13	Metformin + biguanides/sulfonylureas/insulin, dose NR	54.95 ± 8.31	63	NR	NR	A+B: 63	Radical resection
			Biguanides/sulfonylureas/insulin, dose NR	53.77 ± 8.88	113	NR	NR	A+B: 113	Radical resection

NR, not reported; BCLC, Barcelona Clinic Liver Cancer Stage.