What are large bowel and rectal neuroendocrine cancers?

Large bowel and rectal neuroendocrine cancers are rare cancers. They start in the neuroendocrine cells of the large bowel (colon) or back passage (rectum) .  

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 large bowel and rectum are part of our digestive system . The digestive system is large and has more neuroendocrine cells than any other part of the body. So, most neuroendocrine cancers start in the digestive system.

There are 2 key groups of neuroendocrine cancer: 

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

The large bowel (colon)

The colon is about 5 feet long and has 4 sections. Neuroendocrine cancers can start in any of these sections. The parts of the colon are:

• ascending colon – runs up the right side of the tummy (abdomen) and is connected to the small bowel by the caecum

• transverse colon – runs across the body, under the stomach

• descending colon – runs down the left side of the abdomen

• sigmoid colon – an ‘S’ shaped bend that joins the descending colon to the rectum

Large Bowel neuroendocrine cancers can be neuroendocrine tumours (NETs) or neuroendocrine carcinomas (NECs). You can also get neuroendocrine cancer cells mixed in a tumour with a more common type of bowel cancer cell. Doctors call this MiNEN or mixed Neuroendocrine nonNeuroendocrine Neoplasm.

Large bowel neuroendocrine cancers can spread to other parts of the body. The most common places where they can spread to are the:

• liver
• lymph nodes
• the sheet of tissue that lines the wall of the tummy (the peritoneum)

The rectum

The rectum (back passage) starts in the last part of the large bowel. This part of the bowel stores poo (stool) until it is ready to be passed out of the body.

Most rectal neuroendocrine cancers are neuroendocrine tumours (rectal NETs). Rectal neuroendocrine carcinomas (NECs) are less common. You can also get neuroendocrine cancer cells mixed in a tumour with a more common type of rectal cancer cell. Doctors call this MiNEN or mixed Neuroendocrine nonNeuroendocrine Neoplasm.

Rectal NETs are often slow growing and small tumours. But it is possible for them to spread. Around 10 to 20 out of every 100 rectal NETs (around 10 to 20%) may spread to nearby lymph nodes or beyond.

How common are large bowel and rectal neuroendocrine cancers?

Around 370 people are diagnosed with a large bowel or rectal neuroendocrine cancer in England every year.

Rectal neuroendocrine cancers are more common than large bowel neuroendocrine cancers. Doctors often find rectal NETs when people are having tests for something else.

Risks and causes

A risk factor is anything that increases your risk of getting a disease. Different diseases have different risk factors.

Symptoms of large bowel and rectal neuroendocrine cancer

Many people with large bowel or rectal neuroendocrine cancers don’t have symptoms. Doctors often diagnose it when doing tests for something else.

When you do have symptoms, they are usually caused by:

• the growth of the cancer in your large bowel or rectum
• the neuroendocrine cancer spreading to other parts of the body
• hormones made by the cancer, but this is rare for bowel and rectal neuroendocrine cancer

Symptoms might be very similar to bowel cancer symptoms. They might include:

• a change in your normal bowel habits, including diarrhoea or constipation or a change in the consistency of your poo
• pain or discomfort in your tummy, back passage or anus
• bleeding from your bowel or rectum – you might see some blood in your poo, or your poo might look black
• unexplained weight loss, weakness or fatigue

Diarrhoea means having 2 or more loose bowel movements than usual.

Sometimes cancer can block the bowel. This is called bowel obstruction and symptoms of this include:

• griping pain in the tummy
• feeling bloated
• constipation and being unable to pass wind
• feeling sick

A bowel obstruction is an emergency. You should see your doctor quickly or go to A&E if you think you have a bowel obstruction.

Getting diagnosed

Large bowel and rectal neuroendocrine cancers often don’t cause symptoms. Most people are diagnosed with when they are having tests for something else. 

If you have symptoms, you usually see your GP first. They might organise some tests. This might include blood tests and a test to look inside your bowel (colonoscopy).

Your GP will decide if you need to see a specialist.

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
• colonoscopy or sigmoidoscopy to look inside your bowel and take a cancer sample (biopsy )
• CT scan of your chest and tummy
• MRI scan
• Ultrasound scan of your tummy and rectum
• PET-CT scan to show the size of the cancer and whether it has spread
• radioactive scans – these are octreotide scans (or octreoscans ) and MIBG scans

Outlook (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 large bowel and rectal 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.