Mäkelä 1995

Methods	RCT Accrual: 1988 to 1990 Single centre trial Follow‐up: 60 months Setting: tertiary centre
Participants	106 participants (52 men, 54 women) who had "radical primary surgery for CRC" at the Oulu University Hospital (1988 to 1990) Dukes' A: 28 Dukes' B: 48 Dukes' C: 30 Colon primary: 75 Rectal primary: 31 Country: Finland
Interventions	Experimental group: participants who had rectal or sigmoid cancers had flexible sigmoidoscopy with video imaging every 3 months, colonoscopy at 3 months (if it had not been done pre‐operation), then annually. They also had ultrasound of the liver and primary site at 6 months, then annually. Control group: participants who had rectal and sigmoid cancers had rigid sigmoidoscopy and barium enema annually.
Outcomes	Local recurrence Regional recurrence Time to detection of recurrence Recurrence rates Method of detection of recurrence Mode of recurrence Resectability Overall survival
Notes	Radical resection: macroscopic removal of, with microscopically negative margins Local recurrence: restricted to anastomosis and its surrounds Regional recurrence: invasion beyond the site of the primary without distant metastases All participants reviewed at 3, 6, 9, 12, 15, 21, 24, 30, 36, 42, 48, 54, and 60 months At each visit: history, examination, FBC, faecal occult blood test, CEA, CXR performed
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The study provided no more details regarding sequence allocation; therefore, we judged this domain to be at unclear risk of bias.
Allocation concealment (selection bias)	Unclear risk	The study reported no details of allocation concealment, so we judged this domain to be at unclear risk of bias.
Blinding of participants and personnel	Low risk	Participants: not mentioned, but the clear instructions to the participants (see paragraph 4, page 620) about when they were to contact the surgical department meant we judged this domain to be low risk of bias. Assessors: not mentioned, but the protocol for intensive follow‐up was prespecified, as was the process for the minimal group. This would have reduced the risk of bias.
Blinding of outcome assessment	Unclear risk	Participants: not mentioned, but probably not done. This could have been done relatively easily, but was unlikely to have introduced bias. Assessors: not mentioned, but probably not done. This may have introduced bias because the personnel were aware that there were few planned investigations in the minimal group; this may have meant greater weight was placed in reported symptoms in this group. This could be a source of bias.
Incomplete outcome data (attrition and exclusions)	Low risk	The study did not report incomplete outcome data, so we judged this domain to be at low risk of bias (both exclusions and attrition).
Selective reporting (reporting bias)	Unclear risk	Specified in the methods: recurrence (regional and anastomotic), time to detection of recurrence, method of detection of recurrence, surgery for recurrence, survival, synchronous adenomas detected during surveillance Actually reported: time to recurrence, recurrences (local, regional, and distant), method that detected recurrence most frequently, presence of symptoms at recurrence, method of detection of recurrence, surgery for recurrence, survival, survival after radical surgery of recurrence, adenomas detected during surveillance We did not have access to the protocol, so judged this domain to be an unclear risk of bias.
Other sources of bias	Unclear risk	We detected no other bias.