A gastric neuroendocrine tumor (gNET) originates from specialized cells within the stomach lining. These cells are part of the neuroendocrine system, combining features of nerve cells and hormone-producing endocrine cells. When these neuroendocrine cells grow uncontrollably, they form a tumor.
What Are Gastric Neuroendocrine Tumors?
Gastric neuroendocrine tumors develop from neuroendocrine cells in the stomach. These cells produce and release hormones that regulate bodily functions like digestion.
These tumors are broadly categorized into three main types, along with sporadic forms, based on their underlying cause and biological behavior. Type 1 gNETs are the most common, accounting for 70-80% of cases, and are associated with chronic atrophic gastritis, which leads to prolonged high gastrin levels. Type 2 gNETs are less frequent, often linked to Zollinger-Ellison syndrome and multiple endocrine neoplasia type 1 (MEN1), also characterized by elevated gastrin. Type 3 gNETs, the rarest form, arise sporadically, are not associated with high gastrin, and tend to be more aggressive with a higher potential for metastasis.
Symptoms and Diagnosis
Identifying gastric neuroendocrine tumors can be challenging because their symptoms are often non-specific or absent, particularly in the early stages. Individuals might experience vague abdominal pain, nausea, or unintended weight loss. In some instances, gastrointestinal bleeding may occur, manifesting as dark stools or anemia due to slow blood loss. The subtle nature of these symptoms means that many gNETs are discovered incidentally during examinations for unrelated conditions.
Diagnosis relies on a combination of methods. Endoscopy allows direct visualization and biopsies of suspicious areas, with tissue samples then examined under a microscope to confirm origin and grade. Imaging techniques, such as CT scans or MRI, help assess tumor size, location, and spread. Specialized scans, like somatostatin receptor scintigraphy (SRS) or gallium-68 DOTATATE PET scans, are also used to pinpoint tumor locations. Blood tests measuring chromogranin A and gastrin levels, particularly for Type 1 and 2 gNETs, further aid in diagnosis and monitoring.
Treatment Options
Managing gastric neuroendocrine tumors involves a tailored approach, considering the tumor’s specific type, size, grade, and extent of spread. For smaller, less aggressive tumors, especially Type 1 gNETs, active surveillance may be implemented. This involves regular endoscopic examinations and imaging to monitor for any changes, allowing intervention only if the tumor shows signs of growth or aggression. This conservative approach helps avoid unnecessary procedures while ensuring patient safety.
Surgical intervention is a common treatment, with the specific technique depending on the tumor’s characteristics. Endoscopic resection can remove small tumors confined to the stomach lining through an endoscope, avoiding open surgery. For larger or deeper tumors, a partial gastrectomy, which removes a portion of the stomach containing the tumor, may be necessary. In cases where the tumor has spread to nearby lymph nodes or other organs, more extensive surgery might be performed to remove as much cancerous tissue as possible, aiming for complete tumor removal.
Medical therapies are employed for tumors that cannot be surgically removed, have spread, or are more aggressive. Somatostatin analogs, such as octreotide or lanreotide, are commonly used to inhibit tumor growth and hormone secretion, reducing symptoms. Targeted therapies, like everolimus or sunitinib, are options for advanced gNETs, working by blocking pathways involved in cancer cell growth. For highly aggressive or rapidly growing tumors, chemotherapy may be considered to slow tumor progression and control symptoms, often reserved for cases where other treatments are less effective.
Prognosis and Follow-Up Care
The long-term outlook for individuals with gastric neuroendocrine tumors varies considerably, largely influenced by the tumor’s type, its stage at diagnosis, and its grade. Type 1 gNETs generally have a favorable prognosis due to their indolent nature and low metastatic potential. In contrast, Type 3 gNETs, being more aggressive, often carry a less favorable prognosis. The presence of metastasis significantly impacts the long-term outlook.
Following initial treatment, ongoing follow-up monitoring is standard to detect any recurrence or progression. This surveillance includes periodic endoscopic examinations, regular imaging studies like CT or MRI scans to assess for new or growing lesions, and blood tests to measure tumor markers such as chromogranin A. This consistent monitoring helps healthcare providers intervene promptly if changes are detected. The primary goal of this long-term care is to maintain the patient’s quality of life while managing the disease.