The response rate to 131I-MIBG in patients with metastatic PCC/PGL demonstrating 123 I-MIBG avidity was 22% with an estimated 5-year survival of 64%.28 In that study two patients died from myelodysplastic syndrome and one as a result of ARDs, most patients received 1–2 infusions only.28 Notably SDHB- associated PCC/PGL were more likely to respond to 131I-MIBG. The gene discussed is SDHB; the disease is adrenal gland pheochromocytoma.