NCT04174352

FES Imaging to Optimize Tamoxifen for Metastatic Breast Cancer

A Pilot Study of FES Imaging to Optimize Tamoxifen Dose for Metastatic Breast Cancer Patients With ESR1 Mutations

• Status: Recruiting
• Phase: EARLY_Phase 1
• Study type: Interventional
• Enrollment: 12 (estimated)
• Sponsor: University of Wisconsin, Madison · Academic / Other
• Sex: All
• Age: 19 Years
• Healthy volunteers: Not accepted

Summary

Despite broad advancements in endocrine therapy for ERα+ breast cancer, resistance ultimately develops. A common driver of resistance are known ESR1 mutations that lead to constitutively active receptor signaling and transcriptional regulation that is always "turned on" despite the absence of estrogen. Patients with ESR1 mutations are expected to have decreased binding affinity for tamoxifen and thus may be underdosed on standard therapy. \[18F\]-fluoroestradiol Positron Emission Tomography/Computed tomography (FES-PET/CT) imaging is a novel functional imaging technique that can non-invasively measure ERα expression and inhibition in metastatic ERα+ breast cancer. The proposed a pilot study uses FES-PET/CT imaging to measure ERα blockade to determine the optimal dose of tamoxifen in patients with ESR1 mutations.

Conditions

• ERα+ Breast Cancer
• ESR1 Gene Mutation

Interventions

Type	Name	Description
DRUG	Tamoxifen	estrogen modulator
DIAGNOSTIC_TEST	FES PET/CT	Radiolabeled estrogen \[18F\]-fluoroestradiol (FES) in combination with Positron Emission Tomography / Computed Tomography is a molecular imaging technique for measuring pharmacodynamic effects of endocrine therapy. The injected dose of 18F-FES will be 6 mCi (185 MBq) ± 20% with a specific activity greater than 170 Ci/mmol at the time of injection for an activity dose of 6 mCi. Participant will receive baseline imaging and repeat imaging after 3-4 weeks to evaluate for FES blockade as assigned dose level.

Timeline

• Start date: 2020-10-20
• Primary completion: 2026-12-01
• Completion: 2027-12-01
• First posted: 2019-11-22
• Last updated: 2025-12-22

Locations

2 sites across 1 country: United States

Regulatory

• FDA-regulated drug study