Yttrium-90 DOTATOC therapy in GEP-NET and other SST2 expressing tumors: a selected review

Treatment of somatostatin receptor-positive tumors with radiolabeled somatostatin analog is a promising option. Several phase I and phase II studies done at a few centers around the world reported encouraging results with [⁹⁰Y-DOTA-Tyr³]-octreotide (DOTATOC) and/or [(177)Lu-DOTA-Tyr³-Thr⁸]-octreotate (DOTATATE). The current article is a selective review of patients who were treated mainly with ⁹⁰Y-DOTATOC after failure with conventional therapy. The aim is to provide an updated comprehensive evaluation of the overall effectiveness of ⁹⁰Y-DOTATOC therapy in patients with somatostatin-positive tumors. Review of several studies revealed an objective response rate ranging from 20 to 28% for all neuroendocrine tumors (NET)s. For gastroenteropancreatic-NET (GEP-NET), the response rate was found to be consistently better in the range 28-38%. Overall, the cumulative response rate was found to be 24%. An important issue in peptide receptor radionuclide therapy (PRRT) is the dose-response relationship and finding the correct dose of ⁹⁰Y-DOTATOC that will achieve an optimum tumor kill. Nephrotoxicity was common but could be minimized by taking adequate renal protective measures. In conclusion, PRRT remains a good option in patients with inoperable and/or metastatic NETs particularly of GEP origin. Over a decade of experience with ⁹⁰Y-DOTATOC proves that it is still an effective tool for the treatment of large infiltrative NETs with achievement of objective radiological responses in nearly a quarter and disease stabilization in more than half the patients studied so far.