Using PET-CT to find unknown primary cancer sources

[18F]F-FAPI PET-CT to Identify Carcinoma of Unknown Primary Origin

Not applicable Interventional Erasmus Medical Center · NCT06644716

This study is testing a new imaging method to help find the original source of cancer in adults who have been diagnosed with carcinoma of unknown primary origin.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment50 (estimated)
Ages18 Years to 99 Years
SexAll
SponsorErasmus Medical Center Academic / other
Locations6 sites (Amsterdam and 5 other locations)
Trial IDNCT06644716 on ClinicalTrials.gov

What this trial studies

This clinical trial aims to identify the primary tumor in patients diagnosed with carcinoma of unknown primary origin (CUP) using a novel imaging technique called [18F]F-FAPI PET-CT. The study will include 50 patients over the age of 18 who have undergone standard diagnostic procedures but still have no identified primary tumor. Participants will receive a one-time [18F]F-FAPI PET-CT examination at one of six participating medical centers, and the results will be compared with patient follow-up data to assess the effectiveness of this imaging method. The findings will be discussed in a multidisciplinary panel to evaluate the clinical value of the imaging results.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18 and older with histologically-confirmed metastatic disease and no identified primary tumor after standard diagnostic work-up.

Not a fit: Patients with metastasis from a known primary tumor or those with specific types of malignancies such as sarcomas or hematological cancers may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could enable targeted therapies for CUP patients by identifying the primary tumor, potentially improving their treatment outcomes.

How similar studies have performed: While the use of PET-CT in cancer diagnostics is established, the specific application of [18F]F-FAPI for CUP is novel and has not been extensively tested in prior studies.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Age ≥ 18 years old
* Histologically-confirmed metastatic disease without identification of a primary tumor after standard diagnostic work-up, according to the national care pathway for CUP (in Dutch: Regionaal Zorgpad Primaire Tumor Onbekend), which includes at least an \[18F\]FDG PET-CT.

Exclusion Criteria:

* Patients with metastasis from a known primary tumor.
* Sarcomas, melanomas, germ cell tumors, neuroendocrine tumors and haematological malignancies whose exact site of origin is not established.
* History of malignancy within 5 years prior to \[18F\]F-FAPI PET-CT scan, with the exception of the cancer under investigation in this study and malignancies with a negligible risk of metastasis or death (e.g., 5-year OS rate \> 90%), such as adequately treated carcinoma in-situ of the cervix, nonmelanoma skin carcinoma, localized prostate cancer, ductal carcinoma in-situ, or Stage I uterine cancer.
* Prior systemic therapy for the treatment of CUP.
* Radiotherapy prior to \[18F\]F-FAPI PET-CT. Off note: radiotherapy with palliative intent for symptomatic skeleton lesions is allowed.
* Impaired renal function, defined as eGFR (MDRD) \<25 ml/min/1,73 m2. An exception can be made in consultation with the treating physician.
* WHO performance status \>2 (Vademecum).
* Pregnancy/breastfeeding. For the latter, temporary discontinuation may be considered.
* Known allergic reaction to therapeutic radiopharmaceuticals
* Inability to lie still on the back for the duration of PET-CT
* Any (other) condition, disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding that may affect the interpretation of the results, or which might contribute substantially to the patient's experience of study burden (such as non-suppressible claustrophobia)

Where this trial is running

Amsterdam and 5 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Cancer of Unknown Primary[18F]F-FAPIPET-CTDiagnostics
Last reviewed 2026-06-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.