Iodine-131 metaiodobenzylguanidine treatment for metastic carcinoid: Results in 98 patients

BACKGROUND. Iodine-131 metaiodobenzylguanidine (¹³¹I-MIBG) is useful for imaging carcinoid tumors and recently has been applied to the palliative treatment of metastatic carcinoid in small studies. The authors now report their results on the therapeutic utility of high-dose ¹³¹I-MIBG treatment in a large group of patients with metastatic carcinoid tumors. METHODS. The authors performed a retrospective review of 98 patients with metastatic carcinoid who were treated at their institution with ¹³¹I-MIBG over a 15-year period. Endpoints examined included the World Health Organization criteria for treatment response: symptoms, hormone (5-hydroxyindoleacetic acid [5-HIAA]) production, and clinical tumor response. RESULTS. Patients received a median dose of 401 ± 202 millicuries (mCi) ¹³¹I-MIBG. The median survival after treatment was 2.3 years. Patients who experienced a symptomatic response had improved survival (5.76 years vs. 2.09 years; P < 0.01). For the 56 patients who had 5-HIAA levels monitored, the mean urine 5-HIAA levels decreased significantly after ¹³¹I-MIBG treatment (126 ± 122 ng/mL vs. 91 ± 125 ng/mL; P < 0.01); however, the patients with reduced 5-HIAA levels did not experience improved survival (4.11 years vs. 3.42 years; P = 0.2). Patients who received an initial ¹³¹I-MIBG dose > 400 mCi lived longer than patients who received < 400 mCi (4.69 years vs. 1.86 years; P = 0.05). Radiographic tumor response did not predict survival. Toxicity included pancytopenia, thrombocytopenia, nausea, and emesis. CONCLUSIONS. The current data support ¹³¹I-MIBG treatment in select patients with metastatic carcinoid who progress despite optimal medical management. Improved survival was predicted best by symptomatic response to ¹³¹I-MIBG treatment, but not by hormone or radiographic response.