Somatostatinoma: a rare pancreatic and duodenal neuroendocrine tumour

Somatostatinomas are neuroendocrine tumours (NETs). Neuroendocrine cells make and release hormones, and they are found in many parts of the body. In a somatostatinoma the affected cells are those that make the hormone somatostatin. Cancer Research UK explains that somatostatin controls the production of other hormones by the pancreas and also controls how the gut works.

Doctors group NETs according to whether they release abnormal amounts of hormones. Non-functioning NETs release normal levels, whereas functioning NETs release abnormal levels. A somatostatinoma is a functioning NET. It belongs to a family of pancreatic neuroendocrine tumours that also includes insulinoma, gastrinoma, glucagonoma and VIPoma. Non-functioning pancreatic NETs are the most common type in that family, and pancreatic neuroendocrine tumours as a whole need different treatment from the more common type of pancreatic cancer.

Cancer Research UK states that all somatostatinomas are cancers. Some grow slowly and do not spread, whereas others can spread to other parts of the body, most commonly the liver and the lymph nodes. The tumours are also called gastroenteropancreatic NETs (GEP NETs), or pancreatic NETs (pNETs) when they arise in the pancreas.

The pancreas is a large gland that makes digestive juices and hormones. The juices flow down a duct into the duodenum, and the bile duct joins the duodenum right next to the pancreatic duct. More than half of somatostatinomas begin in the pancreas, and most of the remainder begin in the duodenum. More rarely they begin in the jejunum (the middle part of the small bowel), in the cystic duct that connects the gallbladder to the common bile duct, or at the ampulla of Vater, where the bile duct and pancreatic duct meet the duodenum.

Because the tumour is so rare, many doctors will never see one. That is one reason it is common for other, more familiar conditions to be investigated first, and why referral to a team with neuroendocrine expertise matters once a diagnosis is suspected.

Cancer Research UK says some people have no symptoms, or only vague ones. Symptoms caused by the tumour itself can include the following.

• Tummy pain.

• Unexplained weight loss.

• Yellowing of the skin and whites of the eyes (jaundice).

• A bowel blockage (obstruction).

• Bleeding in the bowel or stomach, which may show as blood in vomit or in poo.

Less often, people have symptoms caused by the rise in somatostatin in the body. Doctors call this somatostatinoma syndrome, and it is more common with pancreatic somatostatinomas than duodenal ones. It can cause high blood sugar (diabetes), diarrhoea, gallstones and fatty poo, which may be pale, float and be difficult to flush away.

Cancer Research UK stresses that these symptoms could be due to a somatostatinoma but can also be caused by other, more common conditions, so it is important to have them checked by a doctor. Persistent tummy pain, unexplained weight loss or jaundice should not be left to settle on its own. If you notice blood in vomit or poo, or you develop severe pain, prompt medical advice is appropriate, since bleeding and obstruction are among the symptoms the tumour can cause.

People usually see their GP first. The GP may arrange some tests and decide whether a specialist referral is needed, often to a gastroenterologist. Because somatostatinomas are rare, doctors may check for other conditions first. If cancer is suspected, further tests establish the type of cancer. Once a diagnosis is made, care passes to a team with expertise in treating NETs.

The tests that may be used, according to Cancer Research UK, are listed below. They also show the size of the tumour and whether it has spread, which helps with treatment planning.

• A blood test to measure the amount of somatostatin, and other blood tests to check general health and other substances raised by neuroendocrine cancer.

• Endoscopy to look inside the food pipe, stomach and small intestine and take a biopsy.

• Endoscopic ultrasound, which combines an ultrasound with endoscopy to look at the pancreas and bile ducts.

• ERCP, to look at abnormal areas in the liver, bile duct, pancreas or gallbladder.

• CT and MRI scans.

• Radioactive scans, such as octreoscans, Tektrotyd scans and gallium PET scans.

A pathologist examines a sample of tumour cells and reports how abnormal they look (differentiation) and how quickly they are dividing (grade). Somatostatinomas are well differentiated, meaning the cells look abnormal but still resemble normal neuroendocrine cells. There are 3 grades: grade 1 grows slowly, grade 2 at a moderate speed and grade 3 quickly.

The stage describes the size of the tumour and whether it has spread. Doctors usually use the TNM system or number stages 1 to 4, and the staging approach depends on whether the tumour began in the pancreas or the duodenum.

Cancer Research UK says the cause of most neuroendocrine cancers is not known. Risk factors for pancreatic NETs include inherited conditions such as multiple endocrine neoplasia type 1 (MEN1) and Von Hippel-Lindau disease (VHL), and having a family history of cancer. Having a risk factor does not mean a person will definitely develop cancer. The specialist team also considers whether a person has MEN1, because this may influence treatment decisions.

Surgery is usually the main treatment, although it is not always possible, for example if the tumour has already spread or the person is not well enough for an operation. A multidisciplinary team (MDT) discusses the best approach, taking into account where the tumour is and its size, how many tumours there are, whether it has spread, general health and fitness, and symptoms.

Operations can be open or keyhole (laparoscopic), and an ultrasound scan during surgery may be used to check for other tumours. The type of operation depends mainly on the tumour position and size. Cancer Research UK lists enucleation (removing just the tumour), distal pancreatectomy, pylorus-preserving pancreaticoduodenectomy and the Whipple operation. If the tumour has spread to the liver, the surgeon may remove liver tumours at the same time.

Supportive treatment matters too. Blood sugar is controlled with tablets or insulin injections if it becomes too high, and a dietitian can advise on supplements or tube feeding after significant weight loss.

When surgery is not possible, the tumour has spread or it returns, other treatments can control symptoms but will not remove the tumour. They include somatostatin analogues such as octreotide and lanreotide, peptide receptor radionuclide therapy (PRRT), chemotherapy, targeted drugs such as everolimus and sunitinib and, for liver spread, ablation or liver surgery. A liver transplant is described as a rare option.

After treatment people usually have follow-up appointments, sometimes with blood tests and MRI or CT scans. How often depends on the grade, whether the tumour has spread, the treatment given and any side effects. Contact the team if you have worrying symptoms between appointments.

Cancer Research UK says survival depends on many factors, including the type of NET and its stage, so no one can say exactly how long a person will live, and your doctor is the best person to discuss outlook with you. Not everyone wants to hear statistics, and it is reasonable to say so.

Rare tumours such as this one are normally managed through specialist NHS NET services, usually after discussion by a multidisciplinary team. Private care exists for assessment and some scans, but because treatment is team-based, many people use a combination of routes. Whichever route is used, it is reasonable to ask whether the team regularly treats neuroendocrine tumours and who will coordinate follow-up.