HCCS 2016

HEREDITARY COLON CANCER

Can colon cancer be inherited?

  • About 3% of the population will develop bowel or colorectal(CRC) cancer in their lifetime.
  • The cause is mainly sporadic (random/ as a once off) influenced by environment and lifestyle.
  • In 25% of cases there is at least one family member with CRC cancer.
  • In 6% of these cases the lifetime risk of developing CRC is increased as it is inherited (passed from one generation to the next).
  • Knowing your risk of hereditary CRC is important for your future health as it allows access to healthcare options to reduce the impact of cancer in your life.

What is hereditary colorectal cancer?

  • It is a genetic or inherited condition.
  • When present the risk of developing CRC and other related cancers increases.
  • Two most common forms of hereditary colon cancer include; Familial adenomatous polyposis (FAP), and Hereditary non-polyposis colorectal cancer (HNPCC) or Lynch syndrome.

Differences between FAP and HNPCC


Familial Adenomatous Polyposis (FAP)

Hereditary non-polyposis colon cancer (HNPCC) or Lynch syndrome

Clinical Features

  • 100s of polyps in the colon that develop at an early age (7 and 35 years)
  • Skin, teeth and bone abnormalities may be present
  • Polyps may be present but not in the 100s

Age of Onset

  • Colon cancer develops at a young age usually between 20-25 years
  • Colon cancer will have developed by the age of 40 years
  • Colon cancer develops at a young age, on average 44 years

Risk to develop cancer

  • Increased risk for associated cancers such as small intestine
  • Almost all individuals will develop colon cancer
  • Increased risk for associated cancers such as uterus or stomach
  • Lifetime risk of 80% to develop colon cancer

Download the PDF version of this table


What is the role of genetics in colon cancer?

  • Your body is made up of many cells and each one contains a copy of your genetic material that is made up of genes. Genes carry the information that defines how your body works, looks and develops. You have two copies of every gene as you inherited one from each parent.
  • Faults in certain genes lead to an increased risk to develop cancer.
  • Different genes cause the development of FAP and HNPCC
  • The pattern of inheritance of the gene faults that cause HNPCC and FAP is autosomal dominant
  • Meaning that there is a 50/50 chance of inheriting the faulty gene from a parent.
  • Hereditary colon cancer syndrome occurs equally in males and females.

You are at risk for a hereditary colon cancer syndrome if any of the following is present:

  • You have growths* (polyps/adenomas) in your colon (>10).
  • You were diagnosed with colorectal cancer before age 50 years .
  • You were diagnosed with cancer in the uterus before the age of 50 years .
  • You have a history of colon and other cancers among close relatives from the same side of the family

*Polyps are common - detectable in a large portion of the population by the age of 50 years. Their presence does NOT mean an association with a hereditary colorectal cancer syndrome.

How will genetic counselling help you if you are worried about hereditary colorectal cancer?

  • You will be given information on the role of genetics in the development of colon cancer. A cancer risk model will be used to assess your risk for a hereditary colon cancer in your family.
  • The risk for a hereditary colon cancer will be assessed and used to define the risk for you and your family.
  • Your results will be used to develop a personalised plan for screening, management and genetic testing.
  • The benefits, risks and limitations of these health options will be discussed in an emotionally supportive environment to allow for optimal decision-making for the future.

How knowing your risk for hereditary colon cancer can help you?

  • Access to preventative and management options is defined by your family history and/or the presence of a fault in one of the genes involved in the development of FAP or HNPCC.
  • If your family is considered high risk for hereditary colon cancer, accessing healthcare options such as preventative treatment and more intensive screening may reduce the impact of cancer on your family.

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FAMILIAL ADENOMATOUS POLYPOSIS (FAP)


What is familial adenomatous polyposis (FAP)?

  • Familial adenomatous polyposis (FAP) is a hereditary bowel (colorectal) cancer characterised by multiple (>100) growths (polyps) in the colon.
  • It is diagnosed in about 1 in 8,000 people and makes up 10% of all colorectal cancers (CRC) diagnosed.

What are some of the symptoms of FAP?

  • Multiple colon polyps (>100) that develop from early adulthood and adolescence (average age of onset is 16 years).
  • Almost 100% of people with FAP will develop cancer by the age of 40 years.
  • Presence of other FAP associated cancers such as cancer of the adrenal gland, thyroid, small intestine (duodenal), pancreas, brain or liver.
  • Presence of other features such as lumps in bones (osteomas), skin cysts, abnormal teeth and desmoid tumours.

What is the role of genetics in the development of FAP?

  • FAP results from faults (mutations) in the APC gene.
  • The normal role of the APC gene is to prevent the development of cancer and a mutation in this gene results in the development of cancer.
  • Mutations in the APC gene are inherited in an autosomal dominant manner.
  • In about a 30% of FAP cases the mutation is not inherited but new in the family. The risk to inherit FAP will exist for the next generation.

When should you be concerned about FAP?

  • You have growths* (polyps/adenomas) in your colon (>100).
  • You were diagnosed with colorectal cancer before age 40 years.
  • You were diagnosed with FAP associated cancer before the age of 50 years.
  • Family history of colon and other FAP associated cancers among close relatives from the same side of your family

*Polyps are common - detectable in a large portion of the population by the age of 50years. Their presence does NOT mean an association with a hereditary colorectal cancer syndrome.

How will genetic counselling help you if you are worried about FAP?

  • You will be given information on the role of genetics in the development of FAP.
  • A cancer risk model will be used to assess your risk for FAP in your family and used to define the risk for you and your family.
  • Your results will be used to develop a personalised plan for screening, management and genetic testing.
  • The benefits, risks and limitations of these health options will be discussed in an emotionally supportive environment to allow for optimal decision-making for the future.

Is there a genetic test for FAP?

  • If through genetic counselling you are considered at high risk for FAP you may be offered genetic testing to identify the mutation in the APC
  • gene.
  • Limited genetic testing of the APC gene is available in South Africa but more comprehensive testing is available overseas.
  • Genetic testing is ideally first performed on a family member that has had a diagnosis of cancer.
  • In genetic testing of the APC gene a mutation is found in 90% of cases.

What if no gene mutation is found in the APC gene?

  • If no mutation is identified in the APC gene but your family was assessed as being at high risk for FAP, then you would continue with recommended screening options as for individuals where a mutation was found.

How does knowing your risk for FAP help you?

  • Access to preventative and management options is defined by your family history and/or the presence of a disease-causing change in the APC genes involved in the development of FAP.
  • If your family is considered high risk for FAP, accessing preventative treatment and more intensive screening methods may reduce the impact of cancer on your family.
  • Your risk for FAP can be used to define the risk of FAP for other family members.

What are the recommended screening options for FAP?

  • Annual colonoscopy and/or sigmoidoscopy from the age of 11 to 12 years.
  • Surgical intervention - colectomy at 16 to 30 years.

Please note: These are guidelines and they may differ between specialists. The types of healthcare options/interventions and their timing will be defined by your medical provider.

Need more information about FAP?

Please Contact Us should you need more information about FAP, explore your risk of FAP or make an appointment to determine whether your family is at risk for FAP cancer.

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HEREDITARY NON-POLYPOSIS COLORECTAL CANCER (HNPCC) or LYNCH SYNDROME


What is hereditary non-polyposis colorectal cancer or Lynch syndrome?

  • Hereditary non-polyposis colorectal cancer (HNPCC) is the most common hereditary colorectal cancer (CRC).
  • 3 to 5% of people with CRC have HNPCC.

What are some of the symptoms of HNPCC?

  • Multiple colon growths (polyps) (<100) that develop from early adulthood.
  • Lifetime risk of developing colorectal cancer in families with HNPCC is 50-80% in males and 30-70% in females.
  • Average age of cancer diagnosis is 44 years.
  • Females with HNPCC have a 40-60% risk of developing cancer of the uterus (endometrium).
  • Diagnosis of other associated HNPCC cancers such as stomach cancer.

When should you be concerned about HNPCC?

  • You have growths* (polyps/adenomas) in your colon (<100).
  • You were diagnosed with colorectal cancer before age 44 years.
  • You were diagnosed with an HNPCC associated cancer.
  • You have a family history of colorectal cancer among close relatives, often at an early age and from the same side of your family.
  • You have a family history of related HNPCC cancers such as cancer of the uterus, ovary, urinary tract, stomach, brain and skin.

*Polyps are common - detectable in a large portion of the population by the age of 50years. Their presence does NOT mean an association with a hereditary colorectal cancer syndrome.

What is the role of genetics in HNPCC?

  • HNPCC is caused by faults (mutations) in genes called ‘mismatch repair’ (MMR) genes.
  • The function of these genes is to reduce the risk of cancer development.
  • A mutation in one of these genes increases the chance for CRC and other associated cancers to develop.
  • The common MMR genes involved in the development of HNPCC are MLH1 (50-60%), MSH2 (40%), MSH6 (10%) and others.
  • HNPCC is inherited in an autosomal dominant fashion.
  • The risk for HNPCC is equal for males and females and there is a 50/50 chance of inheriting it from a parent.

How will genetic counselling help you if you are worried about HNPCC?

  • You will be given information on the role of genetics in the development of HNPCC.
  • Various HNPCC risk assessment models (Amsterdam criteria I and II and Bethesda Criteria) will be used to assess the risk of HNPCC in your family.
  • Your results will be used to develop a personalised plan for screening, management and genetic testing.
  • The benefits, risks and limitations of these health options will be discussed in an emotionally supportive environment to allow for optimal decision-making for the future.

Is there a genetic test for HNPCC?

  • Limited genetic testing of the MMR genes is available in South Africa but more comprehensive testing is available overseas.
  • Genetic testing is ideally first performed on a family member that has had a diagnosis of cancer.
  • As there are many genes to test, the genetic testing is guided by combining cancer risk assessment models and other types of tests, which are as follows:
    • A test that confirms that the CRC is as a result of HNPCC and not a sporadic or familial cause.
    • Defines which MMR gene to test for the presence of the gene mutation.
  • Genetic testing is complicated and a mutation may not be detected.

What if no gene mutation is found?

  • If no mutation is identified but your family was assessed as being at high risk for HNPCC, then you would continue with recommended screening options as for individuals where a mutation was found.

How does knowing your risk for HNPCC help you?

  • Access to preventative and management options is defined by your family history and/or the presence of a gene fault involved in the development of HNPCC.
  • If your family is considered high risk for HNPCC, accessing preventative treatment and more intensive screening methods may reduce the impact of cancer on your family.
  • Your risk for HNPCC can be used to define the risk of HNPCC for other family members.

What are the recommended screening options for HNPCC?

  • Two to three yearly colonoscopies from age 20-25 years (or 5 years younger than the earliest diagnosis in the family)
  • Removal of polyps
  • Screening for uterine and ovarian cancer risks
  • Two to three yearly upper endoscopy from the age of 20-35 years because of the duodenal cancer risk

Please note that these are a guideline and may differ between specialists. The types of healthcare options/interventions and their timing will be defined by the treating specialist.

Need more information about HNPCC?

Please Contact Us should you need more information about HNPCC, explore your risk for HNPCC or make an appointment to determine whether your family is at risk for HNPCC.

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