Types of Inherited Colon Cancer

Colon cancer is becoming more common.  There will be around 125,000 new cases diagnosed in America this year.  Many of these cases are in people more than 50 years old and are random.  A small percentage, approximately 10%, however are not random, they have an inherited form of colon cancer.  This could be caused by four different hereditary conditions, hereditary non-polyposis colon cancer, familial adenomatous polyposis, juvenile polyposis (this may also be nonhereditary) and Peutz-Jegher’s syndrome. 

Colon cancer is caused by damage to the genes in your colon cells.  These damages can cause the cells to grow unrestricted.  This unrestricted growth becomes a polyp, which will become cancerous if it’s not removed.  Usually it takes a long time for polyps to develop and even longer to become cancerous.  That’s why colon cancer is rare in people less than 50 years old.  The cases in people less than 50 are frequently caused by an inherited condition. 

Inherited colon cancers are difficult to accurately diagnose.  It is first considered when a person has a strong family history of colon cancer and the affected family members are from separate generations.  For example - a man has two uncles and a cousin that have been diagnosed, this would be a strong family history.  With a bit of research into that patient’s family tree, many more cases of colon cancer may be found and documented. 

The two most common inherited colon cancers are hereditary non-polyposis colon cancer (HNPCC) and familial adenomatous polyposis (FAP).  Recently the genes that cause each of these conditions were identified and now a blood test has been developed that tells you if you have inherited the disease.  Thanks to these blood tests, a person who has inherited the disease can begin getting tested for colon cancer at an earlier age than most people.  This early testing allows physicians to catch the disease in the early stages, when it is most treatable.  It also allows a doctor to determine if a course of chemoprevention is appropriate, or if other prevention strategies are more appropriate. 

Hereditary non-polyposis colon cancer occurs when the gene damage interferes with cell repair.  HNPCC causes about 5% of all colon cancer diagnoses, but it can cause other cancers as well.  HNPCC can also cause cancers in the urinary system (kidney, bladder, or ureter), the female reproductive system (uterus, endometrium, or ovaries), or the rest of the gastrointestinal tract (the stomach, small intestine, or pancreas).  A person with HNPCC has an 80% chance of developing colon cancer.  Even with this high risk, regular checkups and cancer screenings can save your life by preventing or catching cancer early on. 

Familial adenomatous polyposis causes hundreds, even thousands, of polyps to develop in a person’s digestive tract.  Because a person affected by FAP begins developing colon polyps at an early age - he or she often develops colon cancer by age 40, ten years earlier than most physicians even begin screening for it.  This is why it is recommended that people with a family history get the blood test for FAP. 

Not much is known about juvenile polyposis.  Some forms of juvenile polyposis are hereditary, but there isn’t a commercial genetic test yet.  The only test available is used strictly for research purposes.  Juvenile polyposis often causes polyps in the colon and small intestine.  If there are any symptoms present, they are usually caused by the polyps in the colon.  Surgery is often the suggested treatment in such cases. 

Peutz-Jegher’s syndrome is a genetic condition that causes intestinal polyps and freckles on the skin of the mouth.  There are no recorded cases of Peutz-Jegher’s freckles developing into skin cancer.  The main risk of colon cancer comes from the intestinal polyps.  These polyps are usually found in the small intestine and can become so large that they cause an intestinal blockage.  Around half of all Peutz-Jegher’s sufferers require surgery for a blockage by the age of 20.  Peutz-Jegher’s has also been associated with an increased risk of other cancers and it is recommended that all Puetz-Jegher’s sufferers begin cancer screenings at an earlier age than the general population.

Michael Russell

Your Independent guide to Colon Cancer