Colonoscopy plays an important role in detecting colorectal neoplasms in patients with gastric neoplasms

Table 1 Baseline characteristics of included studies

Ref.	Country	Study date	Study type	Patients	Patients in the study group	Evaluation of outcomes	Conclusion	NOS
Chung et al[16], 2017	Korea	January 2009-December 2012	Retrospective case-control study	402	EGC	Colorectal neoplasm and advanced polyps	Colonoscopy plays an important role with respect to the detection of synchronous advanced colorectal neoplasm in patients with EGC	7
Imai et al[11], 2017	Japan	January 2010-December 2012	Retrospective case-control study	390	EGC	High-risk adenomas	Patients with EGC had a significant risk for colorectal cancer	6
Joo et al[12], 2010	Korea	January 2002-December 2008	Retrospective case-control study	372	GN	Adenomatous and cancerous colon polyps	Endoscopists should consider performing routine fiberoptic colonoscopy in patients undergoing endoscopic removal of GNs	7
Kim et al[13], 2022	Korea	January 2015-December 2016	Prospective case-control study	220	EGN	Colorectal adenoma	More stringent colonoscopy surveillance should be considered in elderly patients with EGN	6
Kim et al[17], 2013	Korea	September 2005-August 2010	Prospective case-control study	832	Gastric adenoma or cancer	Colorectal adenoma or cancer	Screening colonoscopy should be considered for gastric adenoma or cancer patients	8
Koh et al[20], 2022	Korea	January 2010-July 2018	Retrospective case-control study	1505	Gastric adenoma or cancer	Adenoma and cancerous colon polyps	Patients with GN are regarded as a high-risk group for colorectal cancer and are recommended for screening colonoscopy at the time of diagnosis	8
Lee et al[14], 2011	Korea	October 2008-September 2010	Prospective case-control study	214	GN	Colorectal neoplasm and high-risk colorectal neoplasm	A screening colonoscopy should be considered in patients with EGN undergoing endoscopic submucosal dissection	6
Lee et al[15], 2011	Korea	July 2005-June 2010	Retrospective case-control study	369	GC	Colorectal neoplasms	Patients with stomach cancer should be regarded as a high-risk group for colorectal neoplasms, and colonoscopy should be recommended for screening	7
Park et al[31], 2010	Korea	November 2004-October 2006	Prospective case-control study	1629	GC	Colorectal neoplasia including colorectal cancer and adenoma	There is a higher prevalence and risk of colorectal cancer in patients diagnosed with GC	9
Yoo et al[32], 2013	Korea	January 2009-December 2010	Prospective case-control study	990	GC	Colorectal neoplasm	Preoperative colonoscopy is strongly indicated in patients with GC	8

GC: Gastric cancer; EGC: Early gastric cancer; GN: Gastric neoplasm; EGN: Early gastric neoplasm; NA: Not applicable; NOS: Newcastle-Ottawa Scales.

Table 2 Baseline characteristics of the gastric neoplasm group and the control group

Characteristics	Studies	Patients (GN group/control group)	Odds ratio/mean difference (95%CI)	Heterogeneity
Age	9	2888/3645	0.73 (0.25, 1.21); P = 0.77	I2 = 0.00%; P = 0.00
Sex
Female	10	Reference	Reference	Reference
Male	10	3012/3776	1.01 (0.91, 1.12); P = 0.85	I2 = 0.00%; P = 1.00
BMI	6	2100/2857	-0.38 (-0.73, -0.03); P = 0.03	I2 = 8%; P=0.03
Diabetes	8	2181/2847	1.08 (0.86, 1.34); P = 0.51	I2 = 35.08%; P = 0.15
Hypertension	3	494/494	0.93 (0.68, 1.27); P = 0.64	I2 = 18.56%; P = 0.29
Alcohol	7	1273/1526	0.99 (0.71, 1.38); P = 0.94	I2 = 75.73%; P = 0.00
Smoking	8	1816/2612	1.32 (0.89, 1.95); P = 0.17	I2 = 86.15%; P = 0.00
Colorectal neoplasms
Size	2	807/897	1.69 (0.77, 2.61); P = 0.22	I2 = 33.22%; P = 0.00
Location
Rectum	5	Reference	Reference	Reference
Colon	5	841/915	1.02 (0.59, 1.77); P = 0.94	I2 = 75.16%; P = 0.00
Pathology
Tubular adenoma	4	Reference	Reference	Reference
Tubulovillous/villous adenoma	4	1066/941	0.54 (0.03, 10.69); P = 0.68	I2 = 97.24%; P = 0.00
Serrated adenoma	4	1066/941	0.23 (0.03, 2.03); P = 0.19	I2 = 83.15%; P = 0.00
Adenocarcinoma	4	1066/941	3.15 (0.25, 39.30); P = 0.37	I2 = 71.58%; P = 0.01
Number > 3	2	460/460	1.50 (0.95, 2.36); P = 0.11	I2 = 0.00%; P = 0.08

GN: Gastric neoplasm; BMI: Body mass index; 95%CI: 95% confidence intervals.

Table 3 Risk factors for colorectal neoplasms among the whole group (including control) and the GN group

Variables	Studies	Participants (GN group/control group)	Odds ratio (95%CI)	Heterogeneity
Whole group
Age	6	1735/1956	1.08 (1.00, 1.17); P = 0.04	I2 = 90.13%; P = 0.00
Male	5	1625/1846	2.31 (1.26, 4.22); P = 0.01	I2 = 87.35%; P = 0.00
BMI	3	944/1165	1.04 (0.82,1.32); P = 0.73	I2 = 0.00%; P = 0.44
Smoking	2	237/367	1.16 (0.70, 1.91); P = 0.57	I2 = 0.00%; P = 0.72
Drinking	2	237/367	1.23 (0.79, 1.92); P = 0.97	I2 = 0.00%; P = 0.35
Diabetes	2	293/293	1.16 (0.40, 3.36); P = 0.79	I2 = 76.42%; P = 0.04
GN group
Age	4	933/1063	2.17 (0.91, 5.17); P = 0.08	I2 = 83.37%; P = 0.00
Male	4	933/1063	1.85 (0.88, 3.90); P = 0.10	I2 = 68.71%; P = 0.02
BMI	3	438/568	0.88 (0.80, 0.98); P = 0.02	I2 =0.00%; P = 0.92
Smoking	3	438/568	1.03 (1.01, 1.05); P = 0.02	I2 = 0.00%; P = 0.57
Drinking	2	237/367	1.36 (0.71, 2.62); P = 0.36	I2 = 0.00%; P = 0.79

GN: Gastric neoplasm; BMI: Body mass index; 95%CI: 95% confidence intervals.