Table 1.
Characteristics of 457 Participants Diagnosed as Having Colorectal Cancer at Age 40 Years or Younger
| Characteristic | No. (%) |
|---|---|
| Sex | |
| Male | 204 (45) |
| Female | 253 (55) |
| Race | |
| White | 382 (84) |
| Black/African American | 11 (2) |
| Hispanic | 7 (2) |
| Asian | 16 (4) |
| Native American | 1 (<1) |
| Middle Eastern | 4 (1) |
| Other | 3 (1) |
| Missing/unknown | 33 (7) |
| Cancer history | |
| 1 CRC only | 389 (85) |
| 1 CRC + other cancer(s) | 34 (7) |
| Synchronous/metachronous CRCs only | 26 (6) |
| Synchronous/metachronous CRCs + other cancer(s) | 8 (2) |
| Site of colorectal cancer | |
| Right colon | 121 (26) |
| Left colon | 105 (23) |
| Rectum | 149 (33) |
| Appendix | 7 (2) |
| Missing/unknown | 75 (16) |
| MSI and MMR IHC statusa | |
| MSI-H and/or abnormal MMR IHC | 47 (10) |
| MSS/MSI-L and/or normal MMR IHC | 279 (61) |
| Missing tumor testing data | 131 (29) |
| Prior genetic testing results (Lynch genes and/or MUTYH)b | |
| Prior genetic testing of ≥1 Lynch genes | 162 (35) |
| Negative result for MLH1 testing | 142 (31) |
| MLH1 VUS detected | 12 (3) |
| Negative result for MSH2 testing | 129 (28) |
| MSH2 VUS detected | 2 (<1) |
| Negative result for MSH6 testing | 40 (9) |
| MSH6 VUS detected | 2 (<1) |
| Negative result for PMS2 testing | 22 (5) |
| PMS2 VUS detected | 1 (<1) |
| Negative result for MUTYH testing | 387 (85) |
| Monoallelic MUTYH mutation detected | 10 (2) |
| MUTYH VUS detected | 0 |
| Recruitment method | |
| Population-based | 314 (69) |
| Clinic-based | 143 (31) |
Abbreviations: CRC, colorectal cancer; MSI, microsatellite instability; MMR IHC, mismatch repair immunohistochemistry testing; MSI-H, high-level microsatellite instability; MSI-L, low-level microsatellite instability; MSS, microsatellite stable; VUS, variant of uncertain significance.
a
No participants had discordant MSI and MMR IHC results.
b
Rows are not mutually exclusive; numerous participants had prior genetic testing for more than 1 gene.