What are small bowel neuroendocrine cancers?

Small bowel neuroendocrine cancers are rare cancers . They start in the neuroendocrine cells of the small bowel .

The small bowel is part of the digestive system . It is also called the small intestine.

Neuroendocrine cells are part of the neuroendocrine system . There are neuroendocrine cells in most organs of our body. They make hormones which control how our bodies work. The digestive system is large and has more neuroendocrine cells than any other part of the body.

There are 2 key groups of neuroendocrine cancer: 

• neuroendocrine tumours (NETs) 
• neuroendocrine carcinomas (NECs) 

The small bowel

The small bowel makes up most of the digestive tract. It is about 6 metres long, but it is folded up so that it fits inside the abdomen.

It has 3 sections:

• duodenum (dew-oh-dean-um) – this is just beyond the lower part of the stomach and is the top part of the small bowel, connecting it to the stomach

• jejunum (jej-you-num) – the middle part

• ileum (ill-ee-um) – the lower part, which connects to the large bowel (colon)

Right at the end of the ileum, just before it joins to the colon, is a small pouch called the appendix.

The term ‘small bowel neuroendocrine cancers’ usually means cancers that develop in the ileum and the jejunum. Some neuroendocrine cancers develop in the duodenum. Doctors sometimes group these separately. And sometimes they include them with neuroendocrine cancers that start in the pancreas. 

How common are small bowel NETs?

Small bowel neuroendocrine cancers are rare. Around 610 people are diagnosed with a small bowel neuroendocrine cancer every year in England.

There are different types of cancer that can start in the small bowel. Around 40 out of 100 (around 40%) of small bowel cancers are neuroendocrine cancers.

Risks and causes

A risk factor is anything that increases your risk of getting a disease. Different diseases have different risk factors. Small bowel neuroendocrine cancers are rare. At the moment, there are no clear risk factors for small bowel neuroendocrine cancer.

Having a family history of cancer is a risk factor for all types of neuroendocrine cancer. This includes small bowel neuroendocrine cancers. Rarely, more than one person in a family develop a small bowel NET, although it is more common for this not to happen. Some people with a small bowel NET develop another small bowel NET in the future.

Symptoms of small bowel neuroendocrine tumours

Not everyone with a small bowel neuroendocrine cancer has symptoms. Doctors often diagnose a stomach neuroendocrine cancer when looking for something else. For example, a doctor might see the cancer on a CT scan which you have for another reason.

If you do have symptoms, they might be unspecific. They can be similar to other conditions that aren’t caused by a neuroendocrine cancer. Symptoms are usually caused by:

• the growth of the cancer in your small intestine or in nearby lymph nodes
• the neuroendocrine cancer spreading to other parts of the body
• hormones made by the cancer

The following symptoms could be due to a small bowel neuroendocrine cancer. But they can also be caused by other medical conditions. It’s important to get them checked out by your doctor.

Symptoms might include:

• tummy (abdominal) pain
• weight loss
• changes to your poo such as diarrhoea
• bleeding in your digestive system – this might cause your poo to be black or blood in your vomit
• feeling or being sick
• feeling very tired

Some small bowel neuroendocrine cancers make hormones that go into the bloodstream. Doctors call these functioning tumours. These hormones can cause symptoms. Doctors call this collection of symptoms carcinoid syndrome. It is more likely to happen if the cancer has spread to other parts of the body, especially the liver. 

The symptoms might include:

• flushing of your skin
• diarrhoea
• wheezing
• fast heart beat

Getting diagnosed

Your cancer might not cause any symptoms. Your doctor might diagnose a small bowel neuroendocrine cancer during tests for something else.

If you have symptoms, you usually see your GP first. They might organise some tests. Your GP will decide if you need to see a specialist. They might refer you to a gastroenterology specialist. These doctors specialise in problems affecting the digestive system. 

If your doctor suspects cancer, you have tests to check the type of cancer you have. Tests also show the size of the cancer and whether it has spread. This helps your doctor plan your treatment.

Tests might include:

• blood tests - these check your general health and check levels of substances raised by neuroendocrine cancer
• urine tests to check for a substance raised by neuroendocrine cancer
• endoscopy – this is to look inside your food pipe, stomach and small intestine and take a cancer sample (biopsy )
• capsule endoscopy - you swallow a small disposable camera inside a capsule which transmits pictures
• colonoscopy to look inside your large bowel and see the end part of your small intestine
• CT scan of your chest and tummy
• MRI scan
• ultrasound scan of your tummy
• PET-CT scan
• radioactive scans – these are octreotide scans (or octreoscans ) and MIBG scans
• echocardiogram – this test checks your heart

Capsule endoscopy

You swallow a small capsule, which contains a camera and light source and takes pictures of the bowel as it travels through. The capsule is the size of a large pill.

Double balloon enteroscopy (DBE)

A DBE is a type of endoscopy. You usually have a capsule endoscopy first and then a DBE as a follow up.

An endoscopist (a specially trained healthcare professional) inserts a small flexible tube, through the mouth or the back passage (rectum). The tube is called a double balloon enteroscope. This allows them to examine the small bowel and take a biopsy if necessary.

You usually have a general anaesthetic and it can take many hours. So doctors don't often use this test.

Survival (prognosis)

The best person to talk to you about your outlook (prognosis ) is your doctor. Not everyone wants to know. People cope differently with cancer and want different information.

Survival depends on many factors. So no one can tell you exactly how long you will live. Your doctor might be able to give you some guide, based on their knowledge and experience.

Your prognosis will depend on whether you have a neuroendocrine carcinoma (NEC) or a neuroendocrine tumour (NET). And it will depend on where it is, and how far it has spread (stage).

Grades, types and stages of small bowel neuroendocrine cancer

The tests and scans you have give information about the type, stage and grade . This helps your doctor decide which treatment you need.