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Table 1. Estimated Relative and Absolute Risk of Developing Colorectal Cancer (CRC)

Family History Relative Risk of CRC [39] Absolute Risk (%) of CRC by Age 79 ya 
No family history14a
One first-degree relative with CRC2.3 (95% CI, 2.0–2.5)9b
More than one first-degree relative with CRC4.3 (95% CI, 3.0–6.1)16b
One affected first-degree relative diagnosed with CRC before age 45 y3.9 (95% CI, 2.4–6.2)15b
One first-degree relative with colorectal adenoma2.0 (95% CI, 1.6–2.6)8b

CI = confidence interval.
aData from the Surveillance, Epidemiology, and End Results database.
bThe absolute risks of CRC for individuals with affected relatives was calculated using the relative risks for CRC [39] and the absolute risk of CRC by age 79 yearsa.


  1. Johns LE, Houlston RS: A systematic review and meta-analysis of familial colorectal cancer risk. Am J Gastroenterol 96 (10): 2992-3003, 2001.  [PUBMED Abstract]