[18F]FET PET for Differentiating Tumor Progression vs Treatment-Related Changes in Brain Metastases (TLX101-Px)

November 5, 2026 updated by: Telix Pharmaceuticals (Innovations) Pty Limited

A Phase 3, Open-label, Single-arm Study to Investigate the Utility of ([18F]FET) PET in Participants With Brain Metastases and Equivocal MRI Findings Following Therapy to Differentiate Between Intracranial Tumor and Treatment-related Changes

This Phase 3 study will evaluate whether [18F]Floretyrosine ([18F]FET) PET imaging can help distinguish active brain tumor growth from treatment-related changes in patients with brain metastases who have unclear MRI findings after treatment. The study has two parts. Part 1 will identify the lowest effective dose of [18F]FET PET that provides reliable imaging results. Part 2 will evaluate the accuracy of [18F]FET PET, using the optimized dose, for distinguishing tumor progression from treatment-related changes. Study results will be compared with information from follow-up imaging, clinical assessments, and, when available, tissue samples obtained during routine clinical care. The goal is to determine whether [18F]FET PET can improve diagnostic accuracy and support clinical decision-making for patients with brain metastases.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
381

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

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

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Adults ≥18 years of age at the time of informed consent.
  • Prior diagnosis of brain metastases from a histologically confirmed solid tumor.
  • At least one measurable intracranial lesion (≥10 mm longest diameter and/or ≥5 mm short axis) identified on MRI and assessed according to RANO-BM criteria.
  • Target lesion considered equivocal for tumor progression versus treatment-related changes on MRI within 1 month prior to Day 1.
  • Prior receipt of CNS-directed therapy for brain metastases within 12 months before Day 1.
  • Planned standard-of-care management including biopsy/neurosurgical intervention and/or clinical follow-up MRI within 2 to 3 months after Day 1.
  • ECOG Performance Status 0-2.
  • Life expectancy of at least 3 months.
  • Willing and able to provide written informed consent and comply with study procedures.

Exclusion Criteria:

  • Serious non-malignant disease that may interfere with study objectives, safety, or compliance.
  • Known hypersensitivity to [18F]FET or tyrosine derivatives.
  • Ongoing Grade 3 toxicity from previous therapies.
  • Exposure to a diagnostic or therapeutic radiopharmaceutical within protocol-specified washout periods.
  • Whole brain radiotherapy or stereotactic radiosurgery within 2 months prior to Day 1.
  • Exposure to another investigational agent within 30 days prior to Day 1 or participation in a conflicting clinical study.
  • Absence of at least one measurable intracranial lesion.
  • Contraindication to PET, CT, or MRI procedures.
  • Inability to undergo required imaging procedures or comply with study requirements.
  • Pregnant or breastfeeding women.
  • Any condition that, in the investigator's opinion, would make the participant unsuitable for the study.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Arm Group Label: [18F]FET PET Imaging
Drug: Floretyrosine F 18 ([18F]FET)

Floretyrosine F 18 ([18F]FET) is an investigational amino acid positron emission tomography (PET) radiopharmaceutical administered as a single intravenous injection for diagnostic imaging. Participants in Part 1 receive 740 MBq (±10%) of [18F]FET to evaluate dose optimization through comparison of reconstructed reduced-dose and full-dose PET images. Participants in Part 2 receive [18F]FET at the optimized dose identified in Part 1 to evaluate its diagnostic performance for differentiating tumor progression from treatment-related changes in brain metastases with equivocal MRI findings following therapy

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Patient-Level Mean Dice Similarity Coefficient for Lesion Spatial Agreement Between Reduced-Dose and Full-Dose [18F]FET PET Images
Time Frame: From Day 1 through Day 2 (±1 day) follow-up

The patient-level mean Dice Similarity Coefficient (DSC), derived from all evaluable lesions, will be used to assess lesion spatial agreement between each reduced-dose [18F]FET PET dataset and the full-dose reference scan. The DSC results will be used to identify the lowest [18F]FET dose demonstrating non-inferior lesion spatial agreement.
From Day 1 through Day 2 (±1 day) follow-up
Sensitivity of [18F]FET PET for Distinguishing Tumor Progression From Treatment-Related Changes Compared With CSOT
Time Frame: From baseline Day 1 through CSOT determination (approximately 2-3 months).

Sensitivity will be assessed for [18F]FET PET at the optimized dose for distinguishing tumor progression from treatment-related changes, using the Composite Standard of Truth (CSOT) as the reference standard.
From baseline Day 1 through CSOT determination (approximately 2-3 months).

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Number of Participants With Adverse Events Following Administration of 740 MBq [18F]FET
Time Frame: From Day 1 through Day 2 (±1 day) follow-up

The incidence and severity of adverse events and other safety findings will be assessed following administration of 740 MBq (±10%) [18F]FET PET
From Day 1 through Day 2 (±1 day) follow-up
Inter-Reader Agreement for [18F]FET PET Classification at the Optimized Dose
Time Frame: Baseline Day 1 through completion of image interpretation following CSOT determination (approximately 2-3 months

Inter-reader agreement will be assessed for interpretation of [18F]FET PET images obtained at the optimized dose.
Baseline Day 1 through completion of image interpretation following CSOT determination (approximately 2-3 months
Lesion-Level Sensitivity of [18F]FET PET for Distinguishing Tumor Progression From Treatment-Related Changes
Time Frame: From baseline Day 1 through CSOT determination, approximately 2-3 months

Sensitivity will be assessed at the lesion level for distinguishing tumor progression from treatment-related changes
From baseline Day 1 through CSOT determination, approximately 2-3 months
Sensitivity of [18F]FET PET Compared With Histopathologic Confirmation
Time Frame: From baseline Day 1 through histopathologic confirmation, approximately 2-3 months

Sensitivity of [18F]FET PET will be assessed using histopathologic confirmation as the reference in participants with available histopathology.
From baseline Day 1 through histopathologic confirmation, approximately 2-3 months
Positive Predictive Value of [18F]FET PET for Tumor Progression Compared With CSOT
Time Frame: From baseline Day 1 through CSOT determination, approximately 2-3 months

Positive predictive value will be assessed for [18F]FET PET classification of tumor progression using the Composite Standard of Truth (CSOT) as the reference standard
From baseline Day 1 through CSOT determination, approximately 2-3 months
Negative Predictive Value of [18F]FET PET for Tumor Progression Compared With CSOT
Time Frame: From baseline Day 1 through CSOT determination, approximately 2-3 months

Negative predictive value will be assessed for [18F]FET PET classification of tumor progression using the Composite Standard of Truth (CSOT) as the reference standard.
From baseline Day 1 through CSOT determination, approximately 2-3 months
Maximum Standardized Uptake Value (SUVmax) of [18F]FET PET Lesions
Time Frame: Baseline Day 1 imaging assessment

SUVmax will be measured for evaluable lesions on [18F]FET PET.
Baseline Day 1 imaging assessment
Mean Standardized Uptake Value (SUVmean) of [18F]FET PET Lesions
Time Frame: Baseline Day 1 imaging assessment

SUVmean will be measured for evaluable lesions on [18F]FET PET.
Baseline Day 1 imaging assessment
Maximum Tumor-to-Brain Ratio (TBRmax) of [18F]FET PET Lesions
Time Frame: Baseline Day 1 imaging assessment

TBRmax will be measured for evaluable lesions on [18F]FET PET.
Baseline Day 1 imaging assessment
Mean Tumor-to-Brain Ratio (TBRmean) of [18F]FET PET Lesions
Time Frame: Baseline Day 1 imaging assessment

TBRmean will be measured for evaluable lesions on [18F]FET PET.
Baseline Day 1 imaging assessment
Number of Participants With Treatment-Emergent Adverse Events (TEAEs) at the Optimized Dose
Time Frame: From Day 1 administration through study completion, approximately 5-6 months

Safety and tolerability at the optimized dose will be assessed by the number of participants experiencing treatment-emergent adverse events (TEAEs), including serious adverse events (SAEs), adverse events leading to treatment discontinuation, and treatment-related adverse events, as applicable. Adverse events will be assessed and graded according to the protocol-specified safety assessment criteria.
From Day 1 administration through study completion, approximately 5-6 months

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Telix Pharmaceuticals (Innovations) Pty Limited

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 (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 1, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 1, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 21, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 5, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 12, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 12, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 5, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
November 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 18F-TLX101-Px-301

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

Yes

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.

Cookie Settings

We use cookies to ensure that we give you the best experience on our website. For more details carefully read our Privacy and Cookies Policy. ...>>>You can change your preferences or withdraw your consent at any time by deleting the cookies from your website or computer as described in the policy. Please accept it and choose your preferences by ticking the corresponding boxes in the "Manage Settings" section below. Please carefully read our Terms of Service before you proceed with using any part of this website.
«Manage Settings