Table 1.

Baseline characteristics for the 271 included patients

Age at diagnosis SPS, mean (SD)	60 (10)
Age at start of prospective follow-up, mean (SD)	62 (9)
Male, n (%)	130 (48%)
Reason first colonoscopy, n (%)
FOBT-based screening	79 (29%)
Primary colonoscopy screening	14 (5.2%)
Familial CRC risk	36 (13%)
Symptoms	110 (41%)
Pain/discomfort abdomen	27/110 (25%)
Rectal blood loss	29/110 (26%)
Altered defecation pattern	29/110 (26%)
Anaemia	6/110 (5.5%)
Unexplained weight loss	2/110 (1.8%)
Other/unknown	32 (12%)
Family history
≥1 FDR with CRC, n (%*)	85/250 (34%)*
≥1 FDR with SPS (WHO 1 and/or 3), n (%*)	11/256 (4.3%)*
WHO SPS classification at inclusion, n (%)
I	99 (36.5%)
III	99 (36.5%)
I and III	73 (27%)
CRC prior to protocolised surveillance phase, n (%)	67 (25%)
Age at diagnosis, median (range)†	61 (19–79)
Multiple CRC, n (%)	16 (24%)
Synchronous	9/16 (56%)
Metachronous	6/16 (37.5%)
Synchronous and metachronous	1/16 (6.2%)
Moment of CRC diagnosis, n (%)†
Prior to clearing phase	40/67 (60%)
During clearing phase	27/67 (40%)
During surveillance, but prior to study inclusion	0
Total number of colonoscopies prior to clearing	523
Per patient, median (range)	1 (0–15)
Total number of clearing colonoscopies	543
Per patient, median (range)	2 (1–9)
Total no. of surveillance colonoscopies prior to inclusion	202
Per patient, median (range)	0 (0–7)
Total number of prospective protocolised surveillance colonoscopies	570
Per patient, median (range)	2 (1–5)
Total years of prospective follow-up	942 patient-years
Per patient, median (IQR)	3.6 (2.3–4.9)

*Percentage refers to patients for whom variable was available.

†In case patients had multiple (metachronous) CRCs, these values refer to the first CRC.

CRC, colorectal cancer; FDR, first-degree relative; FOBT, faecal occult blood test; SPS, serrated polyposis syndrome.