Modelling of tumour initiation rate and tumour progression rate in the three family types (HNPCC, HCC, TCR) in this study compared with sporadic colorectal cancer where no increased initiation and progression are known, and a fourth syndrome, familial adenomatosis polyposis, where an increased initiation rate is well documented for adenomas
| Family type | Tumour initiation | Tumor progression |
|---|---|---|
| HNPCC, hereditary non-polyposis colorectal cancer; HCC, hereditary colorectal cancer; TCR, two close relatives with colorectal cancer; FAP, familial adenomatosis polyposis. | ||
| 0, no increased rate; + (1–5), various degrees of increased rates. This estimation is approximate and only chosen to present the idea of different degrees of increased tumour initiation and tumour promotion rates characterising different families with an increased risk of colorectal cancer because of an inherited predisposition. | ||
| Sporadic colorectal cancer | 0 | 0 |
| HNPCC | + | +++++ |
| HCC | ++ | +++ |
| TCR | +++ | +? (distal adenomas) |
| FAP | +++++ | 0 |