Table 3.2.9 Familial association in the lifetime risk of developing colorectal cancer.

Familial association	Lifetime risk
More than two first degree relatives affected	1:3
Two first degree relatives affected	1:6
One first degree relative aged <45 years affected	1:10
One first degree and one second degree relative affected	1:12
One first degree relative aged >45 years affected	1:17
General population	1:50

Source: Keighley, 2003.³²⁴