Molecular characteristics of colorectal cancer according to tumour location bowel subsite
| Molecular feature | Total N | Caecum | Ascending colon | Hepatic flexure | Transverse colon | Splenic flexure | Descending colon | Sigmoid colon | Rectosigmoid | Rectum | p Value |
| CIMP status | <0.0001 | ||||||||||
| CIMP-low/zero | 1010 (83%) | 160 (78%) | 152 (60%) | 24 (65%) | 54 (70%) | 24 (86%) | 68 (92%) | 266 (96%) | 85 (98%) | 177 (98%) | |
| CIMP-high | 208 (17%) | 44 (22%) | 102 (40%) | 13 (35%) | 23 (30%) | 4 (14%) | 6 (8.1%) | 10 (3.6%) | 2 (2.3%) | 4 (2.2%) | |
| MSI status | <0.0001 | ||||||||||
| MSS | 1061 (84%) | 163 (78%) | 165 (63%) | 27 (71%) | 64 (80%) | 25 (81%) | 70 (93%) | 275 (97%) | 87 (97%) | 183 (98%) | |
| MSI-high | 196 (16%) | 46 (22%) | 98 (37%) | 11 (29%) | 16 (20%) | 6 (19%) | 5 (6.7%) | 8 (2.8%) | 3 (3.3%) | 3 (1.6%) | |
| BRAF mutation | <0.0001 | ||||||||||
| (−) | 1093 (86%) | 186 (88%) | 172 (64%) | 25 (68%) | 62 (78%) | 25 (81%) | 68 (89%) | 276 (96%) | 90 (96%) | 189 (98%) | |
| (+) | 183 (14%) | 26 (12%) | 95 (36%) | 12 (32%) | 18 (23%) | 6 (19%) | 8 (11%) | 11 (3.8%) | 4 (4.3%) | 3 (1.6%) | |
| KRAS mutation | <0.0001 | ||||||||||
| (−) | 819 (64%) | 101 (48%) | 182 (68%) | 26 (70%) | 59 (73%) | 21 (66%) | 50 (66%) | 186 (65%) | 63 (68%) | 131 (68%) | |
| (+) | 458 (36%) | 111 (52%) | 85 (32%) | 11 (30%) | 22 (27%) | 11 (34%) | 26 (34%) | 101 (35%) | 30 (32%) | 61 (32%) | |
| PIK3CA mutation | 0.0016 | ||||||||||
| (−) | 962 (82%) | 146 (75%) | 191 (78%) | 31 (84%) | 62 (85%) | 18 (64%) | 57 (80%) | 220 (83%) | 77 (90%) | 160 (89%) | |
| (+) | 217 (18%) | 49 (25%) | 54 (22%) | 6 (16%) | 11 (15%) | 10 (36%) | 14 (20%) | 44 (17%) | 9 (10%) | 20 (11%) | |
| LINE-1 methylation level (mean±SD) | |||||||||||
| 62.7±9.5 | 63.7±9.0 | 64.7±9.4 | 62.4±8.7 | 62.5±10.0 | 61.9±10.2 | 60.2±11.7 | 61.3±9.1 | 61.0±10.1 | 63.2±8.5 | 0.0003 | |
| ABCB1 expression level (log2 intensity) | |||||||||||
| Median (IQR) | 6.47 (6.35–6.81) | 6.46 (6.35–6.71) | 6.43 (6.35–6.73) | 6.43 (6.35–6.68) | 6.44 (6.35–6.67) | 6.48 (6.38–6.91) | 6.60 (6.36–6.84) | 6.51 (6.37–6.91) | 6.53 (6.35–6.82) | 6.51 (6.39–6.80) | 0.19 |
(%) Indicates the proportion of cases with a specific molecular feature among cancers located in each subsite (caecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectosigmoid or rectum). p Values were calculated by the χ2 test, except for LINE-1 (one-way analysis of variance test) and ABCB1 (Kruskal–Wallis test).
CIMP, CpG island methylator phenotype; MSI, microsatellite instability; MSS, microsatellite stable.