Metformin Use Is Associated with Reduced Incidence and Improved Survival of Endometrial Cancer: A Meta-Analysis

Table 1

Characteristics of the included studies of metformin use and incidence of endometrial cancer.

Study (year)	Region	Study design	Date source	Cases/total subjects	Reference group	Time period	RR (95% CI)	Adjustment variables
Becker et al. 2013 [22]	UK	Case-control study	UK-based General Practice Research Database (GPRD)	291/1746	Nonmetformin	1995–2012	0.88 (0.58, 1.32)	BMI, smoking, and diabetes duration
Luo et al. 2014 [23]	USA	Retrospective cohort study	Women’s Health Initiative	71/4247	Nonmetformin	2005–2010	0.97 (0.60, 1.58)	BMI
Ko et al. 2015 [24]	USA	Retrospective cohort study	Truven Health Analytics’ MarketScan® and Medicare supplemental databases	NR/272411	Nonmetformin	2000–2011	0.89 (0.68, 1.17)	Age, Charlson index, PCOS, endometrial hyperplasia, obesity, combination oral contraceptive use, and ultrasound
Tseng 2015 [18]	Taiwan	Retrospective cohort study	National Health Insurance database of Taiwan	2885/478921	Nonmetformin	1996–2009	0.842 (0.761, 0.931)	Age, hypertension, COPD, stroke, nephropathy, ischemic heart disease, peripheral arterial disease, eye disease, obesity, dyslipidemia, urinary tract disease, other cancers, and other drugs
Franchi et al. 2016 [19]	Italy	Nested case-control study	The healthcare utilization; databases of Lombardy	376/7485	Nonmetformin	1997–2012	1.07 (0.82, 1.41)	BMI

RR, relative risk; 95% CI, 95% confidence interval; NR, not reported; Nonmetformin, patients treated with other hypoglycemic drugs but not metformin.