Family Risks

About 75% of patients with colorectal cancer (CRC) have sporadic disease with no apparent evidence of having inherited the disorder. The remaining 25% of patients have a family history of CRC that suggests a hereditary link. Genetic mutations have been identified as the cause of inherited cancer risk in some colon cancer–prone families; these mutations are estimated to account for only 5% to 6% of CRC cases overall. It is likely that other undiscovered genes and background genetic factors contribute to the development of familial CRC in conjunction with non-genetic risk factors.

Previous History of Cancer

  • Individuals who have previously been diagnosed and treated for CRC are at risk of developing CRC in the future
  • Women who have had cancer of the ovary, uterus, or breast are also at a higher risk of developing the disease 

Hereditary Risk of CRC

Family history of CRC especially in a close relative diagnosed before the age of 45 or multiple relatives affected by the disease. 
The Amsterdam II clinical criteria has been develop to assist clinicians to identify a potential family history:-
3 or more relatives with an associated cancer (colorectal cancer, or cancer of the endometrium, small intestine, ureter or renal pelvis)
2 or more successive generations affected
1 or more relatives diagnosed before the age of 50 years - 1 should be a first-degree relative of the other two
Familial adenomatous polyposis (FAP) should be excluded in cases of colorectal carcinoma

Familial adenomatous polyposis (FAP) is an inherited condition in which numerous polyps form mainly in the epithelium of the large intestine. While these polyps start out benign, malignant transformation into colon cancer occurs when not treated.  FAP carries a near 100% risk of developing colorectal cancer by the age of 40 if untreated however it is a relatively rare condition. FAP can have different inheritance patterns and different genetic causes. Because of the genetic nature of FAP, polyposis registries have been developed around the world. The purpose of these registries is to increase knowledge about the transmissibility of FAP, but also to document, track, and notify family members of affected individuals

Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome
Lynch syndrome is an inherited condition that increases your risk of developing CRC and other cancers. It is also known as hereditary nonpolyposis colorectal cancer (HNPCC).Lynch syndrome is the most common of inherited conditions and it is estimated that about 3 out of every 100 colon cancers are caused by Lynch syndrome. Families that have Lynch syndrome usually have more cases of CRC than would normally be expected. Lynch syndrome also causes CRC to occur at an earlier age than it might do otherwise



Family Risks