18F-FDG Versus 68Ga-FAPI-46 as PET Tracer in ER-positive Breast Cancer.

September 19, 2025 updated by: Maastricht University Medical Center

18F-FDG Versus 68Ga-FAPI-46 as PET Tracer in ER-positive Breast Cancer - a Pilot Study.

The extent of breast cancer is an important prognostic factor in patients diagnosed with this disease. Therefore, adequate staging at diagnosis is a requisite for optimal treatment. In all patients diagnosed with locally advanced breast cancer (LABC), distant staging using 18F-FDG PET/CT is recommended. However, the degree of metabolic uptake in the primary breast tumor is significantly lower in the ER+ subtype compared to HER2+ and triple negative breast cancer (TNBC). As a consequence, a suboptimal 18F-FDG uptake in ER+ breast cancer patients can potentially lead to missed distant metastases. Fibroblast-activating protein inhibitor (FAPI) is a recently developed radiotracer that binds to FAP, a stromal antigen overexpressed in more than 90% of epithelial-derived tumors and their metastases. Previous studies all show 68Ga-FAPI PET/CT to have a higher detection rate compared to 18F-FDG PET/CT. However, all previous studies were performed without considering breast cancer subtype. If the metabolic uptake by 68Ga-FAPI-46 is higher in ER+ breast cancer patients, more lesions will be detected, resulting in a more appropriate treatment for these patients. Therefore, in this pilot study, the investigators aim to compare the diagnostic performance of 18F-FDG with 68Ga-FAPI-46 as PET-tracer in ER+ breast cancer patients.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

20

Phase

  • Phase 2

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Female patient with histopathologically proven ER+ breast cancer.
  • Diagnosed with locally advanced (primary tumor >5 cm and/or presence of axillary lymph node metastases) or recurrent breast cancer, or metastatic breast cancer for which 18F-FDG PET/CT or 18F-FDG PET/MRI staging is performed.
  • Willing and able to undergo the study procedures.
  • Has personally provided written informed consent.

Exclusion Criteria:

  • Age <18
  • Pregnancy
  • Patients with secondary malignancies (except non-melanoma skin cancer)
  • No 18F-FDG PET/CT or 18F-FDG PET/MRI scan.
  • Contra-indications for PET/MRI such as pacemaker, aneurysm clips, metallic device in their body, severe claustrophobia, and severe obesity
  • Chronic inflammatory disease such as rheumatoid arthritis.
  • Patients with severe hepatic or renal impairment (eGFR ≤45mL/min/1.73m²)
  • Inability to provide informed consent.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Additional 68Ga-FAPI-46 PET/CT and PET/MRI exam
All participating patients will undergo an additional 68Ga-FAPI- 46 PET/CT and 68Ga-FAPI-46 PET/MRI scan prior to their breast cancer treatment.
Diagnostic test: 68Ga-FAPI-46 PET/CT and 68Ga-FAPI-46 PET/MRI
All participating patients will undergo an additional 68Ga-FAPI- 46 PET/CT and 68Ga-FAPI-46 PET/MRI scan prior to their breast cancer treatment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
To determine essential input parameters for an adequate sample size calculation for a diagnostic study that compares the diagnostic accuracy of 18F-FDG and 68Ga-FAPI-46 as PET tracer in patients with ER+ breast cancer.
Time Frame: Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.
To investigate the proportion of discordant pairs: the number of lesions detected on 18F-FDG PET but not on 68Ga-FAPI-46 PET and the number of lesions detected on 68Ga-FAPI-46 PET but not on 18F-FDG PET.
Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
To explore the feasibility of taking biopsies in test-positive patients.
Time Frame: Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.
The proportion of 68Ga-FAPI-46-positive 18F-FDG-negative lesions for which performing a biopsy is not feasible.
Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
To investigate the differences in accuracy between 68Ga-FAPI-46 PET/CT versus 68Ga-FAPI-46 PET/MRI.
Time Frame: Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.
Diagnostic performance will be compared between both exams (i.e. 68Ga-FAPI-46 PET/CT and 68Ga-FAPI-46 PET/MRI.
Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.
To provide preliminary estimates of the proportion of 68Ga-FAPI-46-positive and 18F-FDG-positive lesions confirmed as true positives and false positives verified by a histological biopsy (gold standard) in patients with ER+ breast cancer.
Time Frame: Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.
The proportion of 68Ga-FAPI-46-positive lesions and the proportion of 18F-FDG-positive lesions confirmed as true positives or false positives (verified by a biopsy, the gold standard)
Patients will be followed from diagnosis until the additional imaging exams are performed, within 20 working days both PET exams will be performed.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Maastricht University Medical Center

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

September 1, 2025

Primary Completion (Estimated)

March 1, 2027

Study Completion (Estimated)

March 1, 2027

Study Registration Dates

First Submitted

March 11, 2024

First Submitted That Met QC Criteria

March 21, 2024

First Posted (Actual)

March 28, 2024

Study Record Updates

Last Update Posted (Estimated)

September 24, 2025

Last Update Submitted That Met QC Criteria

September 19, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2023-508066-15

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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