Description
The medical management of gastrointestinal neuroendocrine tumors (NETs) involves a tailored approach based on the tumor's grade, stage, and specific hormonal secretion patterns. Somatostatin analogs, such as octreotide and lanreotide, are commonly used to control symptoms related to hormone hypersecretion and to stabilize tumor growth. For well-differentiated NETs with advanced disease, targeted therapies like everolimus and sunitinib may be considered to inhibit mTOR and tyrosine kinase pathways, respectively. Peptide receptor radionuclide therapy (PRRT) with agents like lutetium-177 DOTATATE has shown efficacy in certain cases. Systemic chemotherapy, often with streptozocin-based regimens, may be employed for poorly differentiated or aggressive tumors. Close monitoring through imaging studies, biomarker assessments, and multidisciplinary collaboration between oncologists, endocrinologists, and surgeons is essential for an integrated and individualized approach to the medical management of GI neuroendocrine tumors. Additionally, patient education and support are crucial components to address the chronic nature of this condition and optimize the patient's overall well-being.
Résumé
- Neuroendocrine tumors (NETs) are rare, originating from cells of the diffuse endocrine system, including endocrine glands and cells dispersed throughout the gastrointestinal and respiratory systems. More than half of NET cases arise from the GI tract and respiratory system. These cells receive signals from neurons and secrete hormones into the blood. NETs are a heterogeneous disease with varied extents, tumor burdens, growth rates, grades, and functionality.
- Gastroenteropancreatic (GEP) NETs account for 70% of all NETs, with the small intestine being the most common site (28%), followed by the colon and rectum (30%), appendix (19%), pancreas (8%), and stomach (9%). Retrospective studies show a significant increase in NET incidence due to improved diagnostic techniques and endoscopic ultrasound. Symptoms are often non-specific, mimicking other GI conditions, leading to misdiagnosis and late detection.
- Pathological classification of NETs has evolved, now utilizing the WHO 2019 criteria. Key factors include morphology (well vs. poorly differentiated), immunohistochemical markers (chromogranin A, synaptophysin, CD56), and grading (G1, G2, G3) based on Ki-67 proliferation index. Molecular markers like DAXX, ATRX, RB1, and p53 can aid in difficult diagnoses. Referral to specialized centers is recommended for complex cases.
- The diagnostic approach involves clinical evaluation, biochemical testing (chromogranin A, 5-HIAA), family history assessment (MEN1, MEN2), biopsy analysis, and imaging. Biomarkers are not used for screening, but to follow up on existing diagnoses. Imaging modalities include anatomical (CT, MRI), molecular (dotatate PET scan), and endoscopic (EUS) imaging.
- Management of metastatic NETs focuses on controlling tumor growth and hormone-related symptoms. Somatostatin analogs (octreotide, lanreotide) are commonly used, based on the PROMID and CLARINET trials. Targeted therapies like everolimus (mTOR inhibitor) and sunitinib (VEGF inhibitor) are also options. Peptide receptor radionuclide therapy (PRRT) with lutetium-177 dotatate targets somatostatin receptor 2.
- Immunotherapy is not routinely used in NETs, except in rare cases with microsatellite instability (MSI) or high tumor mutation burden (TMB). Treatment strategies depend on the primary site, grade, patient performance status, co-morbidities, and the need for tumor or symptom control. Adjuvant chemotherapy is considered for resected poorly differentiated tumors, whereas a watch-and-wait strategy is also an option for non-functioning, indolent tumors.
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