Endocrine Abstracts

JOINT1987

Introduction: Pheochromocytomas (PCC) and paragangliomas (PGL) are neuroendocrine tumors arising from chromaffin cells, often presenting with catecholamine hypersecretion. For metastatic or unresectable cases, ¹³¹I-metaiodobenzylguanidine (¹³¹I-MIBG) therapy offers a targeted radiopharmaceutical approach, delivering beta radiation. This case series explores the therapeutic role of ¹³¹I-MIBG in different clinical settings from the experience of our department.

Methods: A retrospective analysis was conducted on five patients diagnosed with PCC or PGL and treated with ¹³¹I-MIBG at our institution. The study includes cases where ¹³¹I-MIBG was utilized as primary therapy, neoadjuvant treatment, or for metastatic disease. Clinical, biochemical, imaging, and treatment outcome data were analyzed.

Case Summaries: • Case 1: A 29-year-old female with metastatic pelvic PGL received four cycles of ¹³¹I-MIBG (28 GBq), leading to tumor shrinkage and enabling surgical resection. No complications were noted.• Case 2: A 41-year-old female with bilateral PCC and pelvic metastasis underwent surgery but had residual disease. Two cycles of ¹³¹I-MIBG (11.1 GBq) achieved complete biochemical and morphological response.• Case 3: A 55-year-old female with recurrent para-aortic PGL received one adjuvant ¹³¹I-MIBG cycle (5.5 GBq) following multiple surgeries. A three-year follow-up showed normal urinary normetanephrines with no reported side effects.• Case 4: A 50-year-old female with inoperable mediastinal and retroperitoneal PGL underwent two cycles of ¹³¹I-MIBG (14.8 GBq), achieving biochemical improvement and stable disease. A third cycle was planned. Side effects were mild (nausea, fatigue).• Case 5: A 48-year-old male with metastatic PCC (liver and bone) received one cycle of ¹³¹I-MIBG (7.4 GBq) post-radiotherapy. He developed pancytopenia five weeks later but recovered.

Results: • Tumor Response: ¹³¹I-MIBG therapy reduced tumor size in some cases, aiding surgical resection, and stabilized disease in others.• Biochemical Outcomes: Significant decreases in urinary catecholamines and metanephrines were observed, with normalization in select cases.• Symptom Control & Safety: Symptoms improved, with manageable side effects (nausea, fatigue, myelosuppression). No hypertensive crises occurred.

Discussion: This case series illustrates the versatility of ¹³¹I-MIBG therapy, demonstrating its role in neoadjuvant, primary, and palliative settings. Tumor downstaging, biochemical response, and symptom control were achieved. A multidisciplinary approach is important in optimizing treatment strategies. Further research is could refine protocols and improve patient selection.

Conclusion: ¹³¹I-MIBG therapy remains an effective treatment for PCC and PGL, offering tumor control, biochemical improvement, and symptomatic relief. This series highlights its use beyond metastatic disease, particularly in neoadjuvant and primary treatment settings.