Metformin and pancreatic neuroendocrine tumors: A systematic review and meta-analysis

Table 2 Characteristics of studies included in systematic review: Metformin as risk factor

Ref.	Country	Period	Design	n	Controls	Male (%)	Mean age (yr)	Outcome measure	95%CI	NOS
Diagnosis
Hassan et al[27], 2008	United States	2000-2006	Retro	160	924	55	54	OR	0.8 (0.3-2.5)	7
Valente et al[29], 2017	Europe	2013-2015	Retro	201	603	51	60	OR	1.4 (0.7-2.7)1 1.5 (0.7-3.4)2	8
Treatment (PFS)
Pusceddu et al[32], 2018	Italy	1999-2015	Retro	445	-	53	59	HR	0.5 (0.3-0.8)	8
Treatment (TFS)
Fan et al[17], 2020	China	2006-2018	Retro	299	-	40	NA	HR	0.8 (0.4-1.6)3 1.3 (0.6-3.0)3	8
Treatment (OS)
Fan et al[17], 2020	China	2006-2018	Retro	299	-	40	NA	HR	0.7 (0.2-2.6)4 0.4 (0.1-2.8)4	8
Awwad et al[37], 2022	Germany	1999-2009	Retro	120	-	NA	58	HR	2.6 (0.7-7.0)5	8

¹No insulin.

²Metformin and insulin.

³Only with metastases.

⁴No metastases

⁵Only patients with metabolic syndrome (n = 32).

NOS: Newcastle–Ottawa Score; OR: Odds ratio; NA: Not available; HR: Hazard ratio; PFS: Progression-free survival; TFS: Tumor-free survival; OS: Overall survival.