Testing the Addition of an Anti-cancer Drug, Triapine, to the Usual Radiation-Based Treatment (Lutetium Lu 177 Dotatate) for Neuroendocrine Tumors

PRIMARY OBJECTIVE: I. To evaluate the safety and to determine the recommended phase 2 dose (RP2D) of lutetium Lu 177 dotatate in combination with triapine. SECONDARY OBJECTIVES: I. To observe and record anti-tumor activity. II. To determine the overall response rate (ORR) by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 at 2, 4, 6, and 8 months post therapy in dose escalation cohort. III. To determine the best overall response rate (ORR) by Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 in dose expansion cohort. IV. To measure duration of response (DOR) associated with the combination. V. To evaluate progression-free survival (PFS), 24-month PFS, and overall survival (OS). CORRELATIVE OBJECTIVES: I. Measure baseline 68 gallium-dotatate (or copper 64 dotatate) biodistribution. II. Evaluate oral triapine plasma pharmacokinetics and corresponding methemoglobin level by venous blood gas proportion. III. Collect blood at baseline and at disease progression to correlate result with clinical outcome. (NOTE: originally this blood was collected to analyze hPG80 but will now the frozen blood samples will be biobanked for future correlative analysis) IV. Describe the tumor molecular profile using whole exome sequencing (WES), as well as ribonucleic acid sequencing (RNAseq) by the National Clinical Laboratory Network (NCLN), and correlate it with treatment outcome. V. Collect plasma for circulating deoxyribonucleic acid (DNA) (ctDNA) assessment. VI. Assess the effect of triapine on single deoxyribonucleoside concentrations by a liquid chromatography-mass spectrometry (LC/MSMS) assay in baseline (pre-treatment) and disease progression blood samples (processed to plasma). OUTLINE: This is a dose-escalation study of triapine followed by a dose-expansion study. Patients receive lutetium Lu 177 dotatate intravenously (IV) for 30 to 40 minutes on day 1 of each cycle and triapine orally (PO) on days 1 throughout 14 of each cycle. Cycles repeat every 56 days for up to 4 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo computed tomography (CT) scan or magnetic resonance imaging (MRI) scan throughout the trial. Patients undergo blood specimen collection on study. Patients are followed up every 3 months for 24 months from the time of enrollment. Patients removed from study for unacceptable adverse event(s) are followed until resolution or stabilization of the adverse event.