Metformin Improves Overall Survival of Colorectal Cancer Patients with Diabetes: A Meta-Analysis

Table 1

Baseline characteristics of included studies in the meta-analysis.

Author	Year	Country	Stage	Range	Follow-up period	Age	Metformin users	Metformin nonusers	Outcome assessment	Confounding variables adjusted
Spillane et al. [17]	2013	Ireland	I–III	2001–2006	1194 person-year	75	207	108	OS, CS	1,2,3,4,5,6,7,8,9
Zanders et al. [20]	2015	Netherlands	I–IV	1998–2011	3.4 years	73.2	666	377	OS	1,2,3,4,6,7,9,10,11,12,
Cossor et al. [19]	2013	USA	I–IV	2005–2010	4.1 years	71	84	128	OS, CS	1,2,
Fransgaard et al. [22]	2015	Denmark	I–IV	2003–2012	5 years	72.3	1962	388	OS	1,2,5,10,11,13,14,15,16,17
Menamin et al. [21]	2015	Northern Ireland	I–IV	1998–2009	4 years	72.1	675	552	OS, CS	2,4,5,6,7,9,10,11,12
Garrett et al. [23]	2012	USA	I–IV	2004–2008	NA	62.7	208	216	OS	1,2,4,17,18
Lee et al. [16]	2011	Korea	I–IV	2000–2008	3.5 years	62.9	258	337	OS, CS	2,4,5,6,7,10,15,19

1: age, 2: tumor stage, 3: tumor grade, 4: year of diagnosis, 5: comorbidity, 6: aspirin use, 7: exposure to nonmetformin ADDs, 8: socioeconomic status, 9: radiation therapy, 10: sex, 11: type of tumor, 12: chemotherapy, 13: ASA score, 14: blood transfusion, 15: smoking, 16: alcohol consumption, 17: BMI, 18: race, and19: HbA1c.