Familial colorectal cancer: A review

Table 1 Relative and absolute risk of developing colorectal cancer according to family history

Family history	Relative risk of CRC	Absolute risk of CRC by age 79
No family history	1	5%1
One first degree relative with CRC	2.25 (95%CI: 2.00-2.53)	11%2
More than one first degree relative with CRC	4.25 (95%CI: 3.01-6.08)	21%2
One first degree relative diagnosed with CRC before age 45	3.87 (95%CI: 2.40-6.22)	19%2

¹Data from the American Cancer Society, August 2013;

²The absolute risk of colorectal cancer (CRC) was calculated using the relative risk and the absolute risk by the age 79.

Table 2 Screening guidelines in familial colorectal cancer

	ACG[6]	ASGE[7]	USMTF[8]
First degree relative with CRC diagnosed at age < 60 or two or more first degree relatives	Colonoscopy at age 40 or 10 yr younger than affected relative; if normal repeat every 5 yr	Colonoscopy at age 40 or 10 yr younger than affected relative; if normal repeat every 5 yr	Colonoscopy at age 40 or 10 yr younger than affected relative; if normal repeat every 5 yr
First degree relative with CRC diagnosed at ≥ 60	Same as average risk	Colonoscopy at age 40 or 10 yr younger than affected relative; if normal repeat every 10 yr	Screening should be at an earlier age (40); individuals may choose to be screened with any recommended form of testing
Second- or third-degree relatives with CRC	-	As average risk individuals	-

CRC: Colorectal cancer; ASGE: American Society for Gastrointestinal Endoscopy; ASG: American College of Gastroenterology; USMTF: US Multi-Society Task Force.

Table 3 Colonoscopy-based screening controlled studies: Risk of advanced adenomas

Design	Age (yr)	No relatives/no controls	AA in relatives/AA in controls	OR	95%CI	Ref.
Prospective, case-control	40-74	185/370	10.8%/4.9%	2.5	1.1-5.4	[32]
Prospective, case-control	40-50	228/220	5.3%/2.3%	2.56	0.87-7.47	[33]
Prospective, cross-sectional	45-75	1252/765	11.3%/6.3%	2.41	1.69-3.43	[39]
Prospective, cross-sectional	40-70	374/374	7.5%/2.9%	3.07	1.50-6.30	[42]

AA: Advanced adenomas; OR: Odds ratio.