Pancreatic neuroendocrine tumor

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at June 28, 2016
StartDiseasesPancreatic neuroendocrine tumor

Also referred to as islet cell carcinoma and pancreatic NETs, pancreatic neuroendocrine tumors (PNETs) are a type of tumor found in the pancreas. Usually, these tumors have a better prognosis than other more common types of pancreatic cancer. Some of these tumors can be removed by surgery which improves a person's prognosis, while others cannot be removed but their growth can be slowed.

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Definition & Facts

Pancreatic neuroendocrine tumors account for less than 5 percent of all pancreatic tumors. They grow as a result of the abnormal growth of hormone-producing cells in the pancreas known as islet cells. Pancreatic neuroendocrine tumors may be malignant or benign, and they generally grow at a slower rate than exocrine tumors (exocrine pancreatic cancer).

Pancreatic neuroendocrine tumors either produce hormones (functional) or produce no hormones (nonfunctional). The functional ones cause an overproduction of hormones by the pancreas, consequently causing a number of hormone-related symptoms. Nonfunctional tumors tend to be cancerous more often than functional tumors.

According to the National Institute of Health, the 5-year survival rate among all patients who have had localized and resected (surgically removed) pancreatic neuroendocrine tumors is 55%. In those with localized pancreatic neuroendocrine tumors that cannot be surgically removed, the five-year survival rate is 15%. The 5-year survival rate for pancreatic neuroendocrine tumors overall is 42%.

Symptoms & Complaints

Most PNETs are functional and thus produce hormones; their symptoms depend on the type of hormone they produce. Tumors that form in the cells that produce the gastrin hormone which produces acid for digestion are called gastrinomas and they cause peptic ulcers and diarrhea. Additional symptoms may include gastroesophageal reflux disease and abdominal pain.

Tumors that form on the cells that produce insulin are called insulinomas. These cause hypogylcemia which is low blood sugar and which subsequently causes confusion, sweating, and tachycardia.

Nonfunctional tumors do not cause any of the hormone-related symptoms seen among functional tumors. A nonfunctional pancreatic neuroendocrine tumor may continue growing for a long time, and typically, these tumors are diagnosed only after the tumor is well advanced. Nonfunctional tumors may even possibly grow quite large, metastasizing or spreading to other body parts before they cause symptoms or complaints like diarrhea, abdominal lumps, indigestion, back pain, or jaundice which is the yellowing of the skin and whites of the eyes.

Causes

Islet cell tumors or neuroendocrine tumors of the pancreas are typically much less common compared to tumors affecting the exocrine tissue in the pancreas. It is unknown what brings about or causes pancreatic neuroendocrine tumors. However, several genetic disorders or syndromes tend to predispose people to pancreatic neuroendocrine tumors.

For example, people who have a family history of the disorder known as multiple endocrine neoplasia type 1 (or MEN1) are generally more prone to getting NETs. Those with this syndrome are more likely to get tumors in the pituitary gland and parathyroid gland as well. Multiple endocrine neoplasias are inherited as autosomal dominant disorders.

Diagnosis & Tests

The diagnostic process begins with the doctor asking the patient a variety of questions about their medical history, family history, and any symptoms. The doctor then performs a physical examination. From there, he or she will order a variety of tests in order to discover the source of the patient's symptoms. Blood tests will be taken. Elevated hormones levels caused by endocrine neoplasms/islet cell tumors can be detected in the blood. Clinical urine tests will also be run.

If cancer is suspected, imaging studies may be performed in order to detect the presence of any growths in the body. These types of tests include X-rays, computed tomography (CT scans) and magnetic resonance imaging (MRIs).

In case the doctor finds or suspects a tumor, the patient may need to undergo further tests to determine the spread, size, and the type of the tumor. Some possible tests include endoscopic ultrasound, biopsy, or somatostatin receptor scintigraphy.

Clinical genetic testing is accessible for various syndromes that increase the risk of cancer, and the testing is best carried out with the assistance of a professional genetic counselor. Individuals diagnosed as having any of these genetic syndromes stand to potentially benefit from increased early screening for tumors.

Treatment & Therapy

Treatment for pancreatic neuroendocrine tumors may include a combination of several approaches. These could be surgery, radiation therapy, hormone replacement therapy, and chemotherapy. Surgical tumor removal is considered to be the most effective treatment for pancreatic neuroendocrine tumors/islet cell tumors.

Patients having functional pancreatic NETs that cannot be removed surgically may benefit from octreotide monthly injections. This is a synthetic hormone that manages hormone-related symptoms caused by functional pancreatic NETs.

External beam radiotherapy is the most common method of radiation therapy which delivers radiation to the body from a machine located outside of the patient. Radiation is used to treat patients subsequent to surgery in order to prevent the recurrence of the tumors (an approach called adjuvant therapy). Radiation may also be recommended for people whose tumors cannot be surgically removed but who are experiencing pain, especially when the tumors have metastasized to the bone.

Several pancreatic neuroendocrine tumors absorb another hormone known as norepinephrine and they may respond to MIBG radiolabeled therapy. With this therapy, the patient gets an intravenous MIBG dose, which is a protein similar to norepinephrine, attached to a substance that is radioactive. The MIBG gets absorbed by the pancreatic NET, allowing the radioactive substance to destroy the tumor cells selectively.

The chance of recovery and treatment options will be dependent on the type of cancer cell, where the tumors are located in the pancreas, if it has spread to other places in the patient’s pancreas or to other body parts. Other factors are the patient’s status in regard to the MEN1 syndrome, age, general health, and if the cancerous growth is newly diagnosed or if it has come back (recurred).

The most important factor when it comes to prognosis is determining if it can or cannot be surgically removed. Other significant prognostic factors for patients having pancreatic endocrine tumor or islet cell tumor include the tumor size, the absence or presence of lymphovascular invasion (in which cancer has spread to the blood vessels and lymph nodes).

Prevention & Prophylaxis

Pancreatic neuroendocrine tumors are not preventable as their causes are linked to genetics.