Table 1.

Characteristics of the included studies

Author	Country	Patients	Age (range, years)	Follow‐up	Sample size (n)	DM (n)	Non‐DM (n)	Study design	Quality assessment
Dominguez‐Ventura et al.11	United States	Pathologic stage I–IV (majority stage I–II)	Median: 82 (80–94)	Median: 2.2 years (range: 1 month–13.6 years)	288	16	272	Cohort study	NOS: 7 stars
Win et al.8	United Kingdom	Pathologic stage I–IIIA	Mean: 69 (42–85)	All patients had at least 3 years and up to 5 years follow‐up	110	12	98	Cohort study	NOS: 7 stars
Bartling et al.12	Germany	Majority T1‐4N0‐1; only 4 had distant metastasis	Median: 68 for DM and 66 for non‐DM group (51–80)	60 months	166	55	111	Cohort study	NOS: 7 stars
Varlotto et al.10	United States	Stage I–IIIB (majority stage I)	Median: 68 (38–96)	Median: 33 months (range: 3–98)	537	96	441	Cohort study	NOS: 7 stars
Fan et al.25	China	Pathologic T1–3N1M0	NA	Median: 53.8 months (range: 1.4–81.8)	199	15	184	Cohort study	NOS: 7 stars
Nakazawa et al.13	Japan	NA	NA	NA	388	69	319	Cohort study	NOS: 6 stars
Washington et al.26	United States	Pathological stage I–IIIA	Median: 67 (21–92)	Median: 30 months (range: 1–149)	957	122	835	Cohort study	NOS: 9 stars
Dhillon et al.15	United States	Pathologic stage I	Mean: 68.5 (21–93)	Median: 44 months	409	71	338	Cohort study	NOS: 7 stars
Jeon et al.27	Korea	Pathologic stage I	NA	Median: approximately 40 months	211	29	182	Cohort study	NOS: 6 stars
Kuo et al.28	Taiwan, China	Pathologic stage I	Mean: 63.9	More than 3 months for each patient	181	48	133	Cohort study	NOS: 6 stars
Jeon et al.9	Korea	Pathologic stage I and II	Median: 64 (32–81)	Median: 40 months	271	42	229	Cohort study	NOS: 6 stars
Medairos et al.16	United States	Pathologic stage I and II	Mean: 69.0	Median: 19.5 months	158	81	77	Cohort study	NOS: 6 stars
Motoishi et al.17	Japan	Pathological stage I–IIIB	Mean: 70.1 (44–88)	Median: 1136 days (range: 11–3598)	468	74	394	Cohort study	NOS: 7 stars

DM, diabetes mellitus; NA, not available; NOS, Newcastle‐Ottawa Scale.