Somatostatinomas - Types, Causes, Symptoms, Diagnosis, and Treatment

Introduction:

Somatostatinomas are rare tumors occurring in the pancreas and the first part of the small intestine called the duodenum. Special cells called delta cells of the pancreas secrete the hormone somatostatin. Somatostatin prevents the release of hormones like insulin, glucagon, gastrin, and cholecystokinin, which manage blood sugars and movement of the gastrointestinal (GI) tract. Excess somatostatin causes an imbalance in these functions, causing symptoms. Though somatostatinomas are cancerous, early diagnosis and treatment with surgery can improve the chances of survival. They are very rare, affecting one in 40 million people. More than 50 percent of the tumors occur in the pancreas, while the rest occur in the duodenum. 75 percent of all cases are cancerous.

What Is the Other Name for Somatostatinoma?

Somatostatinomas are also referred to as functional pancreatic neuroendocrine tumors.

What Are the Types of Somatostatinomas?

Based on where the tumors are located, they are classified into two types, namely:

1. Pancreatic somatostatinomas.

2. Duodenal somatostatinomas.

1) Pancreatic Somatostatinomas:

Pancreatic somatostatinomas occur in the pancreas. Somatostatin is a hormone released by pancreatic cells that stops the functions of hormones like insulin and gastrin, when necessary. When excess somatostatin is produced, it leads to an imbalance in blood sugar levels and gastric mobility.

Sometimes, excess somatostatin causes a condition called somatostatinoma syndrome, which has symptoms like:

• Diabetes (a metabolic disorder that causes high blood sugar levels).

• Cholelithiasis, or gallstones, are cholesterol stones formed in the gallbladder, an organ in the abdomen.

• Steatorrhea or oily stools.

2) Duodenal Somatostatinomas:

Duodenal somatostatinomas occur in the duodenum, the first part of the small intestine.

These types do not produce somatostatinoma syndrome, but the growing tumor causes symptoms. In most cases, the tumor spreads to the liver and lymph nodes, leading to obstruction of parts of the intestine and gallbladder. Obstruction causes symptoms like:

• Swollen and painful abdomen.

• Jaundice or yellowish discoloration of the skin and eyes.

• Diarrhea.

• Blood in stools.

What Are the Causes of Somatostatinomas?

The exact cause of somatostatinomas remains unknown. However, men and women between the ages of 40 to 60 are equally affected. Researchers suggest that about 37 percent of cases are hereditary, which often occur associated with other rare genetic syndromes like multiple endocrine neoplasias (MEN) type 1, neurofibromatosis, and Von-Hippel Lindau syndrome.

What Are the Risk Factors for Somatostatinomas?

The various risk factors for somatostatinomas include:

• Age above 50 years.

• Genetic abnormalities.

• Smoking.

• Alcohol consumption.

• Pancreatitis (a long-standing inflammation of the pancreas).

• Type 2 diabetes.

What Are the Signs and Symptoms of Somatostatinomas?

The symptoms of somatostatinomas usually are very mild in the beginning. As the tumor grows in size, they start to show up. Also, as the symptoms are similar to those of many possible medical conditions, it is important to make an appointment with a doctor who helps in making a correct diagnosis. It also ensures that the other possible causes are detected and treated appropriately.

The following signs and symptoms are noticed in people with somatostatinomas, which include:

1. Abdominal pain (most common symptom).

2. Diabetes occurs due to glucose intolerance (GI), a condition in which the cells do not take up glucose because of insulin deficiency.

3. Loss of weight.

4. Jaundice (a condition in which there is yellowing of the whites of the eye and skin.)

5. Blockage of the bowels.

6. Diarrhea.

7. Steatorrhea or oily and foul-smelling stools.

8. Stones in the gallbladder.

9. Appetite loss.

10. Nausea and vomiting.

Additional symptoms may be present if the tumor has spread to other structures or organs. Symptoms like abdominal pain or bowel blockage occur due to somatostatinomas in the small intestine.

How Are Somatostatinomas Diagnosed?

Doctors order the following tests that help diagnose somatostatinomas, which include blood tests and imaging tests.

Suspected patients are advised to take blood tests, which show extremely high levels of the hormone somatostatin, which is almost 1000 times or higher than normal.

Imaging tests help know the location of the tumor and also whether the tumors have spread to different body parts. Symptoms like abdominal pain, unexplained weight loss, or diarrhea indicate the need for imaging tests. The following tests are advised, which include:

• CT (Computed Tomography) Scan: Cross-sectional images of the body parts are obtained based on several X-rays and computer processing. CT scan helps in detecting tumors in the pancreas and duodenum and also helps in assessing if the tumor has spread to nearby structures.

• MRI (Magnetic Resonance Imaging) Scan: Uses magnetic fields and radio waves to provide precise details of the parts of the body. It is believed that an MRI scan is more useful when compared to a CT scan in detecting small tumors.

• Somatostatin Receptor Scintigraphy: In this technique, the doctor injects a substance known as the somatostatin analog, which is mildly radioactive, into the body. This analog helps in detecting the tumors and also knowing the spread of the tumors.

• Endoscopic Ultrasound: A tube with a camera at the end, guided by an ultrasound scan, is used to study the organs of the abdomen and is used to detect somatostatinomas.

• Biopsy: Biopsy is a tissue sample collected from the suspected area and sent to the laboratory for analysis. Somatostatinomas are confirmed only after biopsy.

How Are Somatostatinomas Treated?

Management of somatostatinomas varies among different patients based on the symptoms. However, the primary form of treatment includes surgery to remove the tumors. In cases where the tumor has spread to different body parts, like the liver, it becomes difficult to treat the tumor with surgery alone. Apart from surgery, a technique called chemo-embolization or hepatic embolization is employed in which a chemical or blood clot is introduced into the artery of the liver, thereby preventing blood supply to the tumor, which makes the tumor cells die. Chemotherapy, a treatment that uses medicines to stop the growth of tumor cells, is also considered a treatment option. Supportive treatment for increased blood sugars and replacement of pancreatic enzymes helps in reducing the symptoms. Nutritional therapies to adjust the fluid, electrolyte, and nutritional deficiencies are also given.

What Are the Survival Rates for Somatostatinoma Patients?

The survival rate following removal of the tumor is more than ten years in 72 percent of the patients. Even for the tumors that have spread, the survival rates are higher when compared to other tumors of the hormone-producing cells.

Conclusion:

The long-term outlook of the condition depends on the early diagnosis and surgery to remove the tumor. Also, cases that have not spread to surrounding tissues have better chances of survival post-treatment. Regular checkups with doctors on a periodic basis are advised to assess the growth of tumors in other body parts. A balanced diet, regular physical activity, and a healthy lifestyle are recommended for patients to cope with the condition.