Complete remission of metastatic pheochromocytoma in (123)I-metaiodobenzylguanidine scintigraphy after a single session of (131)I-metaiodobenzylguanidine therapy: a case report

BACKGROUND: Pheochromocytomas are rare neuroendocrine tumors, with a malignancy frequency of approximately 10%. The treatment of malignant pheochromocytoma is palliative, and the traditional management strategy has limited efficacy. Furthermore, no clear criteria exist for the treatment of metastatic pheochromocytoma, especially for unresectable lesions. We report a case of complete remission of metastatic pheochromocytoma in (123)I-metaiodobenzylguanidine (MIBG) scintigraphy after a single session of (131)I-MIBG therapy. CASE PRESENTATION: A 61-year-old woman had a right adrenal grand tumor and lymph node metastasis on the hilum of the right kidney, both of which incorporated MIBG. After surgery, immunostaining of a tumor specimen showed expression of the tumor makers chromogranin and synaptophysin. One year postoperatively, abdominal computed tomography revealed a local recurrence and retroperitoneal lymph node swelling. The local recurrence was positive for MIBG uptake, whereas the swollen retroperitoneal lymph nodes were negative. She underwent surgery again, but the local recurrence was unresectable because of rigid adhesion to the surrounding tissue. Immunostaining of an intraoperatively extracted swollen retroperitoneal lymph node showed expression of tumor markers. The patient then underwent a single session of (131)I-MIBG therapy (7.4 GBq, 200 mCi), after which the residual lesions no longer incorporated MIBG, and a complete response in (123)I- metaiodobenzylguanidine (MIBG) scintigraphy was achieved. The (131)I-MIBG treatment was repeated 6 months later. None of the lesions were positive for MIBG uptake. CONCLUSIONS: (131)I-MIBG therapy efficaciously treats unresectable lesions that are positive for MIBG uptake.