FES Imaging to Optimize Tamoxifen for Metastatic Breast Cancer
Eligible age
19+ yrs
Accepts
All genders
Locations
1 state
Healthy volunteers
No
See if you qualify for this study
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About this study
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.
Sponsor: University of Wisconsin, Madison
You may qualify if…
- ✓ Participants must have histologically confirmed breast cancer that is metastatic or unresectable with the following:
- ✓ Estrogen receptor expression by immunohistochemistry greater than or equal to 10%
- ✓ ESR1 mutation identified using a Clinical Laboratory Improvement Amendments (CLIA) certified assay via tumor biopsy tissue or circulating free DNA (cfDNA)
- ✓ human epidermal growth factor receptor 2 (HER2) negative
- ✓ Participants must have measurable disease as defined by RECIST 1.1 or evaluable bone disease with at least one lesion measuring 10 mm or greater in size. (Participants with bone and non-bone disease are eligible. One disease site must meet either the measurable or evaluable criteria outlined.) Participants with liver-only disease are not eligible due to the inherent hepatic uptake related to the radiopharmaceutical's hepatobiliary route of elimination.
- ✓ Participants must have received at least 1 prior line of endocrine therapy in the metastatic setting or have had progression within 12 months of adjuvant endocrine therapy. Prior Tamoxifen is allowed in any setting. Prior CDK4/6 in the metastatic setting per NCCN guidelines is allowed.
- ✓ Eastern Cooperative Oncology Group (ECOG) performance status 0-1 (See Appendix A)
- ✓ Life expectancy of greater than 12 weeks.
You may not qualify if…
- ✕ Prior chemotherapy, radiotherapy, targeted, immunotherapy or investigational therapy within 2 weeks or major surgery within 4 weeks of study enrollment or those who have not recovered (to grade ≤ 1 or baseline) from clinically significant adverse events due to agents administered more than 2 weeks earlier (alopecia and fatigue excluded).
- ✕ Participants must not be receiving an ER blocking endocrine therapy (includes fulvestrant, tamoxifen, toremifene, raloxifene) and must be off the agents for a minimum of 60 days prior to planned FES PET/CT to allow for adequate uptake of FES.
- ✕ History of allergic reactions attributed to compounds of chemical or biologic composition similar to those of tamoxifen or \[18F\]-fluoroestradiol.
- ✕ Peripheral neuropathy of severity greater than grade 1.
- ✕ Current optic nerve disorders, retinopathy, lattice degeneration, macular degeneration, retinal vascular disorder, or retinal tears of severity greater than grade 1.
- ✕ History of cerebellar disorders, ataxia, and uncontrolled seizures unless related to transient medical condition and in investigator's opinion is not an active medical issue.
- ✕ History of venous thrombosis/thromboembolic event, including pulmonary embolism and stroke.
- ✕ Have a heart-rate corrected QT interval (using Fridericia's formula) (QTcF) ≥ 470msec or other factors that increase the risk of QT prolongation or arrhythmic events (e.g., heart failure, chronic hypokalemia, family history of long QT interval syndrome).
Where it's recruiting
Madison
Source: ClinicalTrials.gov · NCT04174352 · last updated 2026-07-21