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 screening79 (29%)
 Primary colonoscopy screening14 (5.2%)
 Familial CRC risk36 (13%)
 Symptoms110 (41%)
  Pain/discomfort abdomen27/110 (25%)
  Rectal blood loss29/110 (26%)
  Altered defecation pattern29/110 (26%)
  Anaemia6/110 (5.5%)
  Unexplained weight loss2/110 (1.8%)
 Other/unknown32 (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 (%)
 I99 (36.5%)
 III99 (36.5%)
 I and III73 (27%)
CRC prior to protocolised surveillance phase, n (%)67 (25%)
 Age at diagnosis, median (range)† 61 (19–79)
 Multiple CRC, n (%)16 (24%)
  Synchronous9/16 (56%)
  Metachronous6/16 (37.5%)
  Synchronous and metachronous1/16 (6.2%)
Moment of CRC diagnosis, n (%)†
 Prior to clearing phase40/67 (60%)
 During clearing phase27/67 (40%)
 During surveillance, but prior to study inclusion0
Total number of colonoscopies prior to clearing523
 Per patient, median (range)1 (0–15)
Total number of clearing colonoscopies543
 Per patient, median (range)2 (1–9)
Total no. of surveillance colonoscopies prior to inclusion202
 Per patient, median (range)0 (0–7)
Total number of prospective protocolised surveillance colonoscopies570
 Per patient, median (range)2 (1–5)
Total years of prospective follow-up942 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.