HORMONET: Study of Tamoxifen in Well Differentiated Neuroendocrine Tumors (NET) and Hormone Receptor Positive Expression Abstract #2712

Introduction: We have shown immunohistochemistry (IHC) expression of estrogen (ER) and progesterone receptors (PR) in 20.8% and 18.8% of 96 NET patients (pts). An old clinical trial (Mortel C, 1984) suggested antitumor effects of estrogen/progesterone-directed therapies in NET. Yet the effects of an antiestrogen agent in NET pts whose tumor express ER and/or PR are unknown.
Aim(s): To evaluate the efficacy of tamoxifen in ER/PR+ NET
Materials and methods: Single-arm phase II multicenter trial of tamoxifen 20mg PO continuously until intolerance and/or tumor progression. Eligible pts must be ≥ 18 years old, have histologically confirmed advanced, irresectable well-differentiated lung or gastroeteropancreatic NET, ER and/or PR ≥ 1% IHC expression, progression within 12 months, measurable disease, prior treatments with standard therapies and/or no indication to start new treatment (lack of access, risk of toxicities or who meet criteria for watchful wait), ECOG 0-2, adequate organ function. Exclusion criteria are: concurrent antiestrogen agent, aggressive disease requiring cytotoxic therapy, major surgery in the last 4 weeks, any oncologic therapy in the last 3 weeks, use of oral anticoagulants, previous history of deep vein thrombosis or pulmonary embolism in the last 12 months, postmenopausal vaginal bleeding, synchronous neoplasm. The primary endpoint is disease control rate (DCR) at week 24 by RECIST 1.1. Secondary endpoints are progression-free survival, biochemical and objective response rates. Exploratory evaluations: PET-CT gallium-68 intake intensity variation (at baseline and at week 24). Sample size assumptions: H0 is DCR at week 24 of 50% and H1, 70%; with a type I error of 10%, power of 80% and attrition rate of 30%, the final sample size will be 22 pts
Conference: 17th Annual ENETS Conference 2020 (2020)
Category: Trials in Progress/Trials in Concept
Presenting Author: Prof Rachel Riechelmann

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