A phase II clinical and biological study of lithium carbonate (Li) in patients with low-grade neuroendocrine tumors

e15662 Background: Low-grade neuroendocrine tumors (NETs), such as carcinoid, islet cell tumors, and medullary thyroid carcinomas, respond poorly to chemotherapy, and effective, less toxic therapies are needed. Glycogen Synthase Kinase (GSK)-3β, a multifunctional protein kinase, has been shown to regulate growth and hormone production in NETs. Use of lithium carbonate (Li) in murine models suppressed carcinoid cell growth, reduced GSK-3β levels and reduced expression of chromogranin A. This study assessed the efficacy of Li in patients with NETs. Methods: Eligible pts had pathologically-proven, measurable low-grade NETs. Prior treatment was allowed if completed >4wks prior to registration. Standard eligibility criteria were used, and use of medications affecting Li metabolism or levels were prohibited. A single-arm, open-label, two-stage Phase II design was used. Li was dosed at 300mg orally TID with meals, titrated to a target serum level of 0.8–1.0mmol/L. The primary endpoint was objective tumor respons...