Biomarkers for Endocrine Therapy Resistance in Metastatic Breast Cancer

This study is looking for better ways to tell if endocrine therapy is working for people with metastatic lobular breast cancer (LBC). You may be able to join if you are starting new endocrine therapy for ER/PR-positive (estrogen receptor/progesterone receptor positive) and HER2-negative advanced or metastatic LBC. Researchers will use a special imaging agent called 18F-fluorofuranylnorprogesterone (FFNP) with PET/CT scans, and also collect blood samples (liquid biopsies). They want to see if changes in these measurements after 4 weeks of treatment can predict how well you respond to endocrine therapy. The study aims to find 'biomarkers' (signs in your body) that show if the treatment is effective.

Study design
This is a pilot observational study with 8 participants. It is not specified if it is randomized or blinded.
What's involved
You would have FFNP-PET/CT scans and blood draws (liquid biopsies) at the beginning of the study and again after 4 weeks of treatment.
Compensation
Not stated in the trial record.
Follow-up
The primary endpoints are measured at baseline and 4 weeks, but longer-term follow-up is not specified.

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NCT06067503

Biomarkers to Detect Endocrine Therapy Resistance

Recruiting
PHASE2Ages 18+InterventionalDiagnostic
University of Wisconsin, Madison
~8 participants
Updated 2026-08-25 on ClinicalTrials.gov
What's tested:18F-fluorofuranylnorprogesteroneLiquid BiopsyPositron Emission Tomography/Computed Tomography

At a glance

Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Number of Participants who have decreased FFNP uptake on PET/CT in response to endocrine therapy
Measured over baseline, 4 weeks
+2 more outcomes measured
Metastatic Cancer
Breast Cancer
Lobular Breast Carcinoma
1 sites across 1 states
Wisconsin1
  • Marina Sharifi, MD, PHD · PRINCIPAL_INVESTIGATOR · UW Carbone Cancer Center

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  • Number of Participants who have decreased FFNP uptake on PET/CT in response to endocrine therapybaseline, 4 weeks
  • Number of Participants who have decrease in circulating tumor cell estrogen signaling in response to endocrine therapybaseline, 4 weeks

    Baseline level and on-treatment CTC ESR1 and estrogen regulated gene expression will be evaluated as well as endocrine-resistance associated mutations including ESR1 (though rare in this patient population) and PGR.

  • Number of Participants who have a decrease in concentration of Circulating Tumor DNA in response to endocrine therapybaseline, 4 weeks