|
|
|
Only about 10 percent of all colon cancer is due to hereditary factors. Hereditary colon cancer occurs
when an identifiable gene mutation is passed from generation to generation. This gene mutation is
present in every cell in the body and increases the risk for colon cancer. It’s important for families to
know if they carry the gene so they can receive appropriate cancer screening and take steps to prevent
colon cancer.
Two inherited colon cancer syndromes are Lynch syndrome (also known as hereditary nonpolyposis
colorectal cancer syndrome or HNPCC) and familial adenomatous polyposis (FAP).
- Lynch syndrome is the result of mutations in mismatch repair genes such as MLH2, MSH2 and
MSH6. Mutations in these genes pose an 80 percent risk for colorectal cancer, up to a 60 percent
risk for uterine cancer, a 19 percent risk for stomach cancer, and approximately a 12 percent risk
for ovarian cancer, among others. The average age of colon cancer diagnosis in Lynch syndrome
is 44. Families with Lynch syndrome should have colonoscopies every one to two years beginning
at age 20 to 25, in addition to increased surveillance for other at-risk organs.
- Familial adenomatous polyposis is the result of mutations in the APC gene. Individuals with FAP
have nearly a 100 percent risk of developing colon cancer unless they have preventive surgery.
They develop colon and rectal polyps beginning in the teen years. These families should begin
annual colon screening by colonoscopy or flexible sigmoidoscopy as early as age 10 to 15. When the
polyp burden becomes difficult to manage, they should consider removing the colon.
Familial colon cancer is defined as multiple affected relatives with colon cancer. However, the diagnoses
may not occur at young ages, and the pattern of disease in the family may not be sufficient enough
to diagnose Lynch syndrome, FAP, or other less common syndromes. Despite not meeting hereditary
criteria, these families have an elevated risk for colon cancer. Familial colon cancer may confer
a two- to three-fold risk for colon cancer and screening should be dependent on the number of
affected relatives and the age at which they were diagnosed. In some families, colonoscopies begin
as early as age 40 with follow-up every three to five years, or more frequently if polyps are detected.
The Center for Cancer Genetics at the Curtis and Elizabeth Anderson Cancer Institute is the only facility
in the region that provides risk assessments for families concerned about a hereditary disease.
For more information or to schedule a genetic consultation, call
the Center for Cancer Genetics at 912-350-0926, or make an appointment.
 Next article - Physician Q&A
|
|