Addition of <sup>131</sup>I-MIBG to PRRT (<sup>90</sup>Y-DOTATOC) for Personalized Treatment of Selected Patients with Neuroendocrine Tumors.

Bushnell, David L; Bodeker, Kellie L; O'Dorisio, Thomas M; Madsen, Mark T; Menda, Yusuf; Graves, Stephen; Zamba, Gideon K D; O'Dorisio, M Sue · J Nucl Med · 2021

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Abstract

Peptide receptor radionuclide therapy (PRRT) is an effective treatment for metastatic neuroendocrine tumors. Delivering a sufficient tumor radiation dose remains challenging because of critical-organ dose limitations. Adding <sup>131</sup>I-metaiodobenzylguanidine (<sup>131</sup>I-MIBG) to PRRT may be advantageous in this regard. <b>Methods:</b> A phase 1 clinical trial was initiated for patients with nonoperable progressive neuroendocrine tumors using a combination of <sup>90</sup>Y-DOTATOC plus <sup>131</sup>I-MIBG. Treatment cohorts were defined by radiation dose limits to the kidneys and the bone marrow. Subject-specific dosimetry was used to determine the administered activity levels. <b>Results:</b> The first cohort treated subjects to a dose limit of 1,900 cGy to the kidneys and 150 cGy to the marrow. No dose-limiting toxicities were observed. Tumor dosimetry estimates demonstrated an expected dose increase of 34%-83% using combination therapy as opposed to <sup>90</sup>Y-DOTATOC PRRT alone. <b>Conclusion:</b> These findings demonstrate the feasibility of using organ dose for a phase 1 escalation design and suggest the safety of using <sup>90</sup>Y-DOTATOC and <sup>131</sup>I-MIBG.

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