Table 2a. Molecular characteristics of colorectal cancer cases in the NSHDS cohort.
| N | MSI | MSS | P-value | CIMP-negative | CIMP-low | CIMP-high | P-value | |
|---|---|---|---|---|---|---|---|---|
| Frequency (%) |
197 |
24 (12.2) |
173 (87.8) |
|
97 (50.0) |
70 (36.1) |
27 (13.9) |
|
| Quadruple Index |
|
|
|
0.384 |
|
|
|
0.002 |
| Negative | 89 (51.7) | 9 (42.9) | 80 (53.0) | 52 (61.9) | 31 (50.0) | 6 (23.1) | ||
| Positive |
83 (48.3) |
12 (57.1) |
71 (47.0) |
|
32 (38.1) |
31 (50.0) |
20 (76.9) |
|
|
KRAS |
|
|
|
0.031 |
|
|
|
0.046 |
| Wt | 147 (82.1) | 19 (100.0) | 128 (80.0) | 68 (79.1) | 52 (78.8) | 24 (100.0) | ||
| Mutant |
32 (17.9) |
0 (0.0) |
32 (20.0) |
|
18 (20.9) |
14 (21.2) |
0 (0.0) |
|
|
BRAF |
|
|
|
<0.0001 |
|
|
|
<0.0001 |
| Wt | 161 (82.1) | 13 (54.2) | 148 (86.0) | 93 (96.9) | 57 (81.4) | 8 (29.6) | ||
| Mutant |
35 (17.9) |
11 (45.8) |
24 (14.0) |
|
3 (3.1) |
13 (18.6) |
19 (70.4) |
|
|
PIK3CA Exon20 |
|
|
|
0.448 |
|
|
|
0.670 |
| Wt | 182 (97.8) | 23 (100.0) | 159 (97.5) | 91 (97.8) | 63 (96.9) | 25 (100.0) | ||
| Mutant |
4 (2.2) |
0 (0.0) |
4 (2.5) |
|
2 (2.2) |
2 (3.1) |
0 (0.0) |
|
| PTEN | 1.000 | 0.641 | ||||||
| Normal | 161 (87.5) | 21 (87.5) | 140 (87.5) | 80 (86.0) | 58 (90.6) | 23 (85.2) | ||
| Loss | 23 (12.5) | 3 (12.5) | 20 (12.5) | 13 (14.0) | 6 (9.4) | 4 (14.8) |
Abbreviations: CIMP=CpG island methylator phenotype; MSS=microsatellite stable; NSHDS=Northern Sweden Health Disease Study; MSI=microsatellite instability; Wt=wild-type.
The following numbers of missing cases were present in NSHDS: CIMP status, 3; Quadruple Index, 25; KRAS mutation status, 18; BRAF mutation status, 1; PIK3CA mutation status, 11; PTEN mutation status, 13. Cases lacking nuclear staining of tumour cells for at least one of MLH1, MSH2, MSH6 or PMS2 were considered to have a positive MSI screening status (MSI). CIMP according to an eight-gene panel including CDKN2A, hMLH1, CACNA1G, NEUROG1, RUNX3, SOCS1, IGF2 and CRABP1; CIMP-negative, 0 genes hypermethylated; CIMP-low, 1–5 genes hypermethylated; CIMP-high, 6–8 genes hypermethylated. Kruskall–Wallis test was used for continuous variables, χ2-test or Fisher's exact test used for categorical variables.