1	exp colon cancer/ or exp rectum cancer/	172220
2	(colorectal adj3 (neoplas* or cancer? or tumour? or tumor? or carcinoma?)).ti,ab.	97898
3	(colon* adj3 (neoplas* or cancer? or tumour? or tumor? or carcinoma?)).ti,ab.	75721
4	(bowel adj3 (neoplas* or cancer? or tumour? or tumor? or carcinoma?)).ti,ab.	5761
5	(rectal adj3 (neoplas* or cancer? or tumour? or tumor? or carcinoma?)).ti,ab.	26610
6	(rectum adj3 (neoplas* or cancer? or tumour? or tumor? or carcinoma?)).ti,ab.	5978
7	1 or 2 or 3 or 4 or 5 or 6	234787
8	carcinoembryonic antigen/	25911
9	cea.ti,ab.	22520
10	(carcinoembryonic adj3 antigen?).ti,ab.	13394
11	(carcinoembryonic adj3 antibod*).ti,ab.	657
12	(carcino‐embryonic adj3 antigen?).ti,ab.	617
13	(carcino‐embryonic adj3 antibod*).ti,ab.	21
14	8 or 9 or 10 or 11 or 12 or 13	36255
15	cancer recurrence/ or tumor recurrence/	119064
16	recurrent disease/ or relapse/	192303
17	recur*.ti,ab.	523223
18	relaps*.ti,ab.	174290
19	exp treatment failure/	82867
20	Reoperation/	53394
21	follow up/ and (postoperative care/ or postoperative period/)	38038
22	reoperat*.ti,ab.	31321
23	((local or distant) adj2 failure).ti,ab.	4986
24	((therap* or treatment or surg*) adj3 fail*).ti,ab.	83522
25	((therap* or treatment or surg*) adj3 (respond* or response*)).ti,ab.	167374
26	((postoperat* or post‐operat* or postsurg* or post‐surg* or posttreat* or post‐treat* or posttherap* or post‐therap*) adj5 follow up).ti,ab.	23063
27	((postoperat* or post‐operat* or postsurg* or post‐surg* or posttreat* or post‐treat* or posttherap* or post‐therap*) adj5 surveillance).ti,ab.	1797
28	((postoperat* or post‐operat* or postsurg* or post‐surg* or posttreat* or post‐treat* or posttherap* or post‐therap*) adj5 monitor*).ti,ab.	4961
29	15 or 16 or 17 or 18 or 19 or 20 or 21 or 22 or 23 or 24 or 25 or 26 or 27 or 28	1107887
30	7 and 14 and 29	2994
31	(meta‐analysis or systematic review or MEDLINE).tw.	144743
32	7 and 14 and 31	78
33	30 not 32	2952