Table 1.

Characteristics of included studies.

study	design	tumor stage	size	treatment or metformin exposure in study group	intervention in control group	HR(95% CI)
Ambe 2015	RCS	resectable	44	ongoing metformin use	never used metformin	0.54(0.16–1.86)
Amin 2016	RCS	all stages	1916	use in the 6 months prediagnosis.	diabetic medications other than metformin	0.88(0.81–0.96)
Cerullo 2016	RCS	resectable	3396	use following surgery	no use after surgery	0.79(0.67–0.93)
Chaiteerakij 2016	RCS	all stages	980	ever use	ever use	0.93(0.81–1.07)
Choi 2016	RCS	LA; metastatic	349	unclear	unclear	0.70(0.49–1.99)
Hwang 2013	RCS	LA; metastatic	516	use at any time in the peridiagnosis period	no use during peridiagnosis period	1.11(0.89–1.38)
Kordes 2015	RCT	LA; metastatic	121	GE + metformin	GE + placebo	1.05(0.72–1.55)
Kozak 2016	RCS	resectable	171	continuous use from first consult to discharge postsurgery	never use or discontinued use	0.60(0.21–1.67)
Lee 2016	RCS	all stages	237	cumulative use ≥ 1 month post-diagnosis	use < 1 month or never use	0.61(0.46–0.81)
Reni 2016	RCT	metastatic	60	PEXG + metformin	PEXG	1.56(0.87–2.80)
Sadeghi 2012	RCS	all stages	302	ever use	never use	0.64(0.48–0.86)

Abbreviations: RCS = retrospective cohort study; PA = pancreatic adenocarcinoma; peridiagnosis period = between 6 months prediagnosis and one month postdiagnosis; GE = gemcitabine + erlotinib; PEXG = cisplatin + epirubicin + capecitabine + gemcitabine; all stages = resectable + locally advanced + metastatic; LA = locally advanced.