Wang 2009

Methods	RCT Accrual dates: Jan 1995 to March 2001 Setting: teaching hospital Follow‐up: 64 to 79 months
Participants	326 participants (177 men and 149 women) who had had curative resection for colorectal cancer Stratified for location (colon or rectum) and Dukes' stage. Dukes' A: 53 Dukes' B: 186 Dukes' C: 93 Country: China
Interventions	Experimental arm: colonoscopy at each visit Control arm: colonoscopy at six months, , 30 months, and 60 months from randomisation
Outcomes	Overall survival (5‐year survival and HR) Postoperative cancer (anastomotic, extraluminal recurrence, and metachronous primaries) CRC deaths Salvage surgery Asymptomatic recurrences Major colonoscopy complications
Notes	All participants had clinic visits 3/12 for 12/12, 6/12 for 24/12, then 12/12 for 24/12. At each visit, history and examinationwas performed, as well as CEA, CXR, and liver imaging (CT or US). In each group, more investigations and examinations were performed if symptomatic. Curative resection: no macroscopic residual and clear pathological margins All recurrences were confirmed histologically. Local recurrence were divided into anastomotic (intraluminal recurrence within 5 cm of the initial primary) and extraluminal. Metachronous: second primary colorectal cancer after exclusion of a synchronous primary by a preoperative colonoscopy or within 6 months postoperatively Salvage surgery was considered curative when all macroscopic was removed and pathological margins were clear. doi: 10.1016/j.gie.2008.05.017
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (page 610): "The patients were then randomized to either the RCS group or the ICS group by means of sealed envelopes containing cards printed with ICS or RCS within each stratum." Comment: the paper gave insufficient details of the randomisation process.
Allocation concealment (selection bias)	Unclear risk	Quote (page 610): "Sealed envelopes containing cards printed with ICS or RCS within each stratum..." Comment: there is insufficient detail given to be sure that allocation concealment was truly concealed; it is not stated who performed the randomisation and if the envelopes were opaque.
Blinding of participants and personnel	High risk	The study did not mention blinding of participants or personnel. Participants in the control arm may have been more likely to report symptoms knowing that they were not having colonoscopies.
Blinding of outcome assessment	High risk	Quote (page 610): "More complete and systematic examinations were performed whenever a patient in either group had symptoms suggestive of a possible recurrence of the disease (e.g. abdominal or perineal pain, altered bowel movements, change in fecal colour, weight loss)." Comment: lack of blinding may have introduced bias with assessment of reported symptoms or signs, perhaps making further investigation more likely in the control group.
Incomplete outcome data (attrition and exclusions)	Unclear risk	Quote (page 611): "Seven patients (ICS, 4; RCS, 3) were lost during the follow‐up period." Comment: the paper gave no details about why they were lost to follow‐up, which may introduce bias.
Selective reporting (reporting bias)	Unclear risk	Outcomes stated in the paper Survival Local recurrence Distant metastases Metachronous CRC Anastomotic recurrences Intraluminal recurrences Extraluminal recurrences Outcomes reported OS CRC deaths Postoperative CRC (local recurrences and metachronous) Time to relapse Asymptomatic recurrence Salvage surgery Adverse outcomes We did not have access to the study protocol, so rated the risk of bias for this outcome as unclear.
Other sources of bias	Unclear risk	We detected no other bias.