MUTYH-associated polyposis (MAP) is a rare genetic condition that increases the risk of developing certain types of cancer, most notably colon cancer. It is caused by an alteration in the mutY DNA glycosylase (MUTYH) gene, which is involved in DNA damage repair. People with MAP often develop between 10-100 polyps within the colon, however it can also develop in areas of the small intestine.
Familial cancer syndromes, also known as hereditary cancer syndromes, are rare conditions that cause an increased risk of cancer as the result of inherited genetic mutations in certain cancer-related genes. They can affect both adults and children, however they generally develop in people at a younger age than normal. While familial cancer syndromes are not classified as cancer, they are equally as severe and can be life-threatening as they are associated with the development of various tumours throughout the body. Having a familial cancer syndrome does not guarantee the development of cancer, however the risk of developing cancer is higher than those who do not have a familial cancer syndrome.
MAP is generally diagnosed equally among the sexes, and is often diagnosed between the ages of 40-60. However, anyone can develop this disease.
MAP Related Tumours
MAP is most commonly associated with the development of colorectal cancers, however it has also been linked to other types of tumours. Some examples include:
- Colorectal (bowel) cancer.
- Small bowel cancer, most commonly in the duodenum.
- Ovarian cancer.
- Bladder cancer.
- Skin cancer, most commonly sebaceous carcinoma.
The following tumours may also have an increased incidence in people with MAP, however more research is needed to confirm:
- Breast cancer.
- Breast cancer (Male).
- Endometrial cancer.
- Stomach (gastric) cancer.
- Pancreatic cancer.
- Thyroid cancer.
Treatment
When cancers are detected, they are staged and graded based on size, metastasis, and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. However, each patient with MAP will present with a unique disease behaviour, with varying tumour locations and symptoms. As such, there is no one treatment method that will work for everyone, and there is no standard staging system for this disease. Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:
- Type of tumours present.
- Whether the tumours are malignant (cancerous) or benignnot cancerous, can grow but will not spread to other body parts (non-cancerous).
- Tumour location.
- Whether or not malignant tumours have metastasised.
- Your age.
- General health.
- Your treatment preferences.
Your doctor may also recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment options for tumours associated with MAP may include:
- Surgery to remove as much of the tumour(s) as possible – this will vary based on location.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Cancer Screening
Once a diagnosis of MAP has been confirmed, implementing a targeted screening plan becomes essential due to the increased risk of developing certain cancers. The content of this plan will vary from person to person based on the genetic mutation involved, your family’s history of cancer and the types of cancers that may be present. It will also outline the routine tests you should have and how regularly you should have them. Some recommendations for MAP may include:
- Annual physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Colonoscopyan examination of the large intestine/bowel with a small, flexible instrument known as a colonoscope every 1-2 years starting at age 25-30.
- Gastroscopyexamination of the stomach and part of the small bowel with a small, flexible instrument known as a gastroscope starting at age 30-35 (suggested frequency in literature ranges from three months to four years).
- Annual thyroid ultrasounda type of medical imaging that uses soundwaves to create detailed images of the body in patients at risk of thyroid cancer.
Screening options for MAP may evolve as new technologies are developed and our understanding of the condition grows. It is essential to discuss your individual circumstances with your healthcare team to determine the most appropriate screening plan for you.
Risk factors
MAP is caused by a genetic mutation in the mutY DNA glycosylase (MUTYH) gene, which is involved in DNA damage repair. It is an autosomal recessive disorder, which means that you have to inherit one gene with the mutation from both parents in order to develop the condition. If both of parents carry the gene, there is a one in four chance of a child having the condition.
Symptoms
The symptoms of MAP often vary by the type(s) of tumours present. General symptoms of MAP may include:
- The presence of 10 to 100 colorectal polyps.
- Abdominal pain and/or discomfort.
- Changes in bowel movements, potentially including:
- Diarrhoea.
- Constipation.
- Feeling of incomplete bowel movement.
- Thin bowel stools.
- Blood in stools.
- Rectal bleeding.
- Unexplained weight loss/loss of appetite.
- Fatigue.
- Anaemiaa condition where there aren't enough red blood cells in the blood, causing fatigue, weakness and pale skin and affecting how the body responds to infection.
- Nausea and/or vomiting.
Symptoms related to specific tumours can be found on our knowledgebase.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have tumours associated with MAP they may order some of the following tests to confirm the diagnosis and refer you to a specialist for treatment. The tests required for diagnosis will often vary based on the symptoms present, and where the tumour(s) are suspected to be located.
- Physical examination.
- Genetic testing.
- Pelvic examination.
- Digital rectal examinationan examination conducted by a urologist where a finger (or digit) is inserted into the rectum to feel for abnormalities of the anus, rectum or prostate (DRE).
- Blood teststesting done to measure the levels of certain substances in the blood.
- Imaging tests, potentially including:
- Ultrasound.
- MRI (magnetic resonance imaging)a type of medical imaging that uses radiowaves, a strong magnet and computer technology to create detailed images of the body.
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- Exploratory procedures, such as:
- Colonoscopy.
- Flexible sigmoidoscopyexamination of the lower portion of the large intestine and rectum with small, flexible instrument known as a sigmoidoscope .
- Other types of endoscopya procedure that involves inserting a long, flexible tube with a light and small camera (endoscope) into the body to view internal organs as indicated.
- Biopsyremoval of a section of tissue to analyse for cancer cells.