Neuroendocrine tumors (NETs) are cancers originating from specialized cells with nerve and hormone-producing characteristics. Small intestine neuroendocrine tumors develop in the small intestine. While often slow-growing, they can be serious and may spread to other parts of the body.
What Are Small Intestine Neuroendocrine Tumors?
Small intestine neuroendocrine tumors originate in the neuroendocrine cells lining the small intestine, specifically in the duodenum, jejunum, and ileum. While relatively uncommon, with an incidence of approximately 1 in 100,000 people annually, their diagnosed incidence has increased in recent decades, possibly due to improved diagnostic methods.
These tumors are categorized into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). Well-differentiated NETs tend to resemble normal cells and grow at a slower rate, sometimes producing hormones. NECs are more aggressive, grow quickly, and are less differentiated. Small intestine NETs often produce substances like serotonin and tachykinin peptides, which can lead to various symptoms. They frequently spread to the mesenteries, the tissue that anchors the small bowel, and the liver.
Recognizing the Symptoms
Symptoms of small intestine neuroendocrine tumors can be varied and often nonspecific, making diagnosis challenging. These symptoms can arise from the tumor’s growth, its spread to other areas, or the hormones it produces. Abdominal pain is a common symptom, which can be persistent and located in the lower abdomen. This pain may be caused by the tumor growing or potentially blocking the intestines.
Diarrhea is another frequent symptom, often with chronic or watery stools, sometimes accompanied by flushing of the skin. This combination, along with wheezing and a fast heartbeat, can indicate carcinoid syndrome, which is more likely to occur if the cancer has spread, particularly to the liver. Other general symptoms include unexplained weight loss, chronic fatigue, and gastrointestinal bleeding, which may present as dark, tarry stools or blood in vomit.
Diagnostic Procedures
Diagnosing small intestine neuroendocrine tumors involves a combination of tests to pinpoint the tumor’s location, size, and characteristics. Initial evaluation often includes a physical examination and a review of the patient’s health history. Laboratory tests are used to measure hormone levels and other substances in the blood or urine.
Specific diagnostic procedures include:
Blood tests: Check for chromogranin A (CgA), a protein released by NETs, often elevated in 60-80% of digestive system neuroendocrine tumors.
24-hour urine test: Measures levels of 5-HIAA, a breakdown product of serotonin.
Imaging tests: Provide visual information about the tumor. These include computed tomography (CT) scans and magnetic resonance imaging (MRI), with MRI often preferred for detecting liver metastases.
Functional imaging: Such as somatostatin receptor PET/CT or PET/MRI, uses a tracer that binds to receptors on neuroendocrine cells, helping to locate tumors that express these receptors.
Biopsy: Involves removing tissue for microscopic examination to confirm a cancer diagnosis and determine its specific features. This tissue sample can also be tested for genetic or protein markers to guide treatment.
Treatment Strategies
Treatment for small intestine neuroendocrine tumors is tailored to the individual, considering the tumor type, grade, stage, and the patient’s overall health. Surgical removal of the tumor is often the primary treatment, especially if the cancer has not spread. The goal of surgery is to remove the affected part of the small bowel and regional lymph nodes, and sometimes to debulk or remove as much of the tumor as possible even if it has spread.
For patients with metastatic disease or when surgery is not feasible, various medical therapies are employed:
Somatostatin analogs: Medications like octreotide or lanreotide are often first-line for both functional and nonfunctional metastatic small bowel NETs. These medications help control symptoms by reducing hormone secretion and also have anti-proliferative effects.
Targeted therapies: Everolimus, an mTOR inhibitor, is used for advanced neuroendocrine tumors, including those that have spread.
Peptide Receptor Radionuclide Therapy (PRRT): Using agents like Lutetium-177 (177Lu-Dotatate), this delivers targeted radiation directly to tumor cells that express somatostatin receptors, aiming to shrink tumors and improve progression-free survival.
Chemotherapy: An option particularly for poorly differentiated neuroendocrine carcinomas (NECs), which are more aggressive and typically respond better to platinum-based regimens like cisplatin or carboplatin with etoposide.
Liver-directed therapies: Such as hepatic artery embolization or percutaneous ablation, may be used for liver-dominant disease to manage symptoms and reduce tumor burden.
Long-Term Management and Outlook
Long-term management of small intestine neuroendocrine tumors involves ongoing monitoring and follow-up care to track disease progression and manage symptoms. After initial treatment, patients typically undergo regular radiographic and biochemical surveillance, often every 6 to 12 months for at least 10 years. This continued oversight helps detect any recurrence or spread early.
The prognosis for small intestine neuroendocrine tumors can vary, with 5-year survival rates estimated to be around 85% for small bowel NETs and a median survival exceeding 8 years. Factors influencing prognosis include the stage of the disease at diagnosis, with localized disease having a significantly higher 10-year survival rate (around 95%) compared to distant metastases (around 10%). The tumor’s grade, which indicates how fast the cancer cells are growing, also plays a role, with slower-growing NETs generally having a better outlook than faster-growing NECs. Despite contemporary treatments, patients may experience impaired quality of life, including issues with sleep, bowel function, depression, and vitality. Symptom management, including addressing diarrhea and other hormonal effects, remains a focus of ongoing care to improve the patient’s overall well-being.