Gastrinomas are gastrin-secreting tumors that predominantly occur in the duodenum.
The duodenum (the first of the three divisions of the small intestine) is located above the stomach and before the jejunum (central division of the small intestine) where the majority of chemical digestion transpires.
The name duodenum is derived from the Latin duodenum digitorum, which literally means “twelve fingers’ breadths”.
Rarely, gastrinomas are found in the stomach, pancreas, jejunum, peripancreatic lymph nodes, various ectopic sites, splenic hilum, omentum, ovary, liver, gallbladder, and the common bile duct.
More than 50% of gastrinomas are malignant and can spread or grow into regional lymph nodes and/or the liver. Multiple Endocrine Neoplasia (MEN) type I, hyperparathyroidism, and pituitary adenomas are related to 25% of all gastrinoma generation, but often result in tumors that take a more benign path.
A triad of disorders that frequently accompany one another are tumors of the pancreas (gastrinomas), hypergastrinemia (an excess of gastrin in the blood), and severe ulcer disease compose the eponym Zollinger-Ellson Syndrome or ZES.
Common Signs and Symptoms
The anomalous secretion of gastrin results in hyperplasia (the abnormal proliferation of cells composing a tissue) of fundic parietal cells and increased levels of basal acid. These level increases often lead to Severe Ulcer Disease (part of the ZES triad), resulting in abdominal pains and diarrhea which are the primary indicators that a gastrinoma and/or gastrinoma related ulceration is present in the body.
Patients with gastrinomas experience many of the same symptoms as indiculas with common ulcers. Gastrinomas, however, affect the blood with much higher levels of gastrin than common ulcer disease does. Thus, gastrinomas are usually diagnosed by measuring gastrin levels in the blood. If a gastrinoma is present, gastrin levels are typically 4 – 10 times higher than normal levels.
Gastrinomas are difficult to locate surgically, but can easily be identified by introducing certain foods into a patient’s diet and/or injecting them with secretin which almost always provokes a gastrin increase in persons with gastrinomas, but rarely does in individuals without them.
Locating gastrinomas is effectively accomplished using radionuclide octreotide scanning (also known as somatostatin receptor scintigraphy). Radionuclide octreotide scanning is a type of x-ray that produces far greater results than magnetic resonance imaging (MRI) and computed tomography (CT scan) according to many studies.
Because many gastrinomas are malignant, surgical removal of the tumor is frequently advised. Surgery can completely cure the overproduction of gastrin in many patients, but remains controversial with patients suffering from the triad of disorders that compose ZES. The benefits of surgery in patients with ZES are unclear.
Drug treatment can drastically reduce the production of gastrin, but rarely results in complete freedom from the symptoms of gastrinoma. These drugs are rigidly regimented and typically prescribed indefinitely, for the briefest discontinuation in treatment can cause severe ulcer recurrence.
The drugs of choice for treating gastrinomas are known as proton pump inhibitors of gastric acid. Such drugs will reduce gastrin levels, creating an environment conducive for ulcer healing.
The symptoms of gastrinoma can usually be controlled with medical therapy. Surgery, however, may or may not result in a complete cure. Approximately 50% of patients with ZES in whom the gastrinoma is not or cannot be removed will host a malignant tumor that will ultimately result in death. 42% of patients in whom the tumor is removed are disease-free in one year and 35% are disease-free at five years, according to a NIH study.
About 25% of patients with gastrinomas have liver metastases at the time of diagnosis. If the malignant gastrinoma has metastasized in the liver, the patient’s chances of survival for five years after the diagnosis is reduced from 905 to 20-30%. The life expectancy of patients with gastrinomas that are localized within the lymph nodes can be as long as 25 years after diagnosis, without any indications of further tumor spread.