Large bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines neuroendocrine tumours (NETs), also known as NETs of the large intestine, are rare tumours that develop in the large bowel, the long, hollow, tube that is the last part of the gastrointestinal tract. It is composed of three main sections – the caecum, colonthe longest portion of the large bowel that absorbs water and salts from ingested food, and rectumthe last section of the large intestine/bowel that holds waste until it is ready to be removed from the body.
Neuroendocrine cancers are a complex group of tumours that develop in the neuroendocrine system, which is responsible for regulating important bodily functions such as heart rate, blood pressure and metabolism. They most commonly develop in the gastro-intestinal tract, pancreasa long, flat organ that sits between the stomach and the spine that plays a key role in digestion and blood sugar regulation, and the lungs; however, they can develop anywhere in the body. These tumours develop from neuroendocrine cellsthe basic structural and functional unit of all living things, which are responsible for receiving signals from the nervous system and producing hormones and peptides (small proteins) in response.
Large bowel NETs are diagnosed equally among the sexes, and tend to be diagnosed in people over 50. However, anyone can develop this disease.
Types of Large Bowel Neuroendocrine Tumours
There are two primary types of large bowel NETs, which are categorised by their location within the large bowel.
Colon Neuroendocrine Tumours
Colon NETs are a very rare type of NET that develops in the colon, the largest, middle portion of the large bowel. These tumours are often large and aggressive, and are often likely to metastasise. Colon NETs can have a good prognosisto predict how a disease/condition may progress and what the outcome might be when caught early.
Rectal Neuroendocrine Tumours
Rectal NETs are a common type of large bowel NET that develops in the rectum, the end portion of the large bowel that connects to the anusthe opening where solid waste (faeces or stool) exits the body. In many cases, rectal NETs are asymptomatic, and are often found by accident. As they are asymptomatic, they are often diagnosed at a late stage of disease, and may have metastasised. Rectal NETs can have a good prognosis.
Treatment
If a large bowel NET is detected, it will be staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumoura tissue mass that forms from groups of unhealthy cells) indicates the size and depth of the tumour.
- N (nodea small lump or mass of tissue in your body) indicates whether the cancer has spread to nearby lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissuea group of cells that work together to perform a function.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localisedaffecting only one area of body cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advancedat a late stage, far along or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may 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. This is often performed after a biopsyremoval of a section of tissue to analyse for cancer cells, and can help guide treatment options for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for large bowel NETs may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
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- Endoscopic mucosal resectiona minimally invasive procedure that uses an endoscope to remove cancer or abnormal growths/tissue from the lining of the gastrointestinal tract.
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- Right or left hemicolectomyremoval of a portion of the colon; can be the right side (right hemicolectomy) or the left side (left hemicolectomy).
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- Sigmoid colectomysurgery to remove the sigmoid colon.
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- Colectomycomplete or partial removal of the colon.
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- Proctocolectomysurgical removal of the colon and rectum.
- Somatostatin analogues (SSAs)medication used to inhibit excessive hormone production .
- 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, potentially including peptide receptor radionuclide therapy (PRRT)a targeted cancer treatment that uses radioactive substances (radionuclides) to deliver radiation directly to tumour cells.
- Targeted therapymedication that targets specific molecular features of 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.
Risk factors
Because of how rare large bowel NETs are, there has been little research done into the riskthe possibility that something bad will happen factors of this disease.
Symptoms
Some people with large bowel NETs will appear asymptomatic in the early stages of disease. As the tumour progresses, some of the following symptoms may appear:
- Changes in bowel habits, potentially including:
- Diarrhoeafrequent discharge of watery or loose stools from the body.
- Constipationa condition where a person has difficulty passing faeces/stools.
- Feeling of incomplete bowel movement.
- Thin bowel stools.
- Rectal bleeding or bloodthe red bodily fluid that transports oxygen and other nutrients around the body in stools.
- Stools that appear darker in colour, often black.
- Abdominal pain, bloating and/or cramping.
- Anal and/or rectal pain.
- Unexplained weight loss.
- Fatiguea state of extreme tiredness or exhaustion, can be physical or mental.
- 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.
- Bowel obstructiona complete or partial blockage of the bowel/intestines.
- Carcinoid syndrome (rare), which carries its own set of symptoms:
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- Facial flushing (usually red or purple in the face, neck, and/or upper chest).
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- Diarrhoea.
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- Wheezing.
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- Abdominal pain.
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- Carcinoid heart disease (plaques on the heart muscle caused by excess hormonea chemical substance produced by glands in the endocrine system that regulates various functions in the body production).
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- Fatigue.
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- Skin changes, such as red or purple spots on the face, neck, and/or upper chest.
- Paraneoplastic syndromesa group of rare disorders that occur when the immune system has a reaction to a cancerous tumour within the body (rare).
- Hypercalcaemiaexcess levels of calcium in the blood (rare).
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 a large bowel NET, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Faecal occult blood test (FOBT)a test used to determine if there is any trace of blood present in faeces or stool.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
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- 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.
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- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
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- PET (positron emission tomography) scana type of medical imaging that uses radioactive tracers to create detailed images of the body.
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- Barium studiesa type of x-ray where barium powder is either swallowed (barium swallow) or introduced via the colon (barium enema) to coat the organs of the digestive tract and provide clearer x-ray images.
- Colonoscopyan examination of the large intestine/bowel with a small, flexible instrument known as a colonoscope.
- Biopsy.