# ZIRCON

Source: https://nuclide.cc/trials/zircon/  
Nuclide record `zircon` (Trial). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A single PET scan with a radioactive antibody (89Zr-girentuximab, brand TLX250-CDx) can tell whether an unexplained kidney lump is a clear cell kidney cancer before surgery, so some patients might be spared an unnecessary biopsy or operation.

## Summary

ZIRCON was a prospective, open-label, multicentre phase 3 trial across 36 sites in nine countries that evaluated [89Zr]Zr-girentuximab PET-CT, a radiolabelled monoclonal antibody targeting carbonic anhydrase IX (CAIX), in patients with an indeterminate renal mass (cT1, up to 7 cm) scheduled for nephrectomy. Patients received a single dose (37 MBq, 10 mg girentuximab) five days before abdominal PET-CT, and blinded central histopathology from the resected specimen served as the reference standard.

Of 371 patients screened, 300 received the tracer and 284 were evaluable for the primary analysis. Mean sensitivity was 85.5% and mean specificity was 87.0%, both exceeding the prespecified thresholds for all three independent readers; performance was maintained in the cT1a (up to 4 cm) subgroup. Safety was favourable, with most adverse events attributable to the subsequent surgery rather than the tracer.

The result supports use of CAIX PET as a non-invasive complement to cross-sectional imaging for risk-stratifying small renal masses, potentially reducing biopsies and overtreatment of benign lesions. TLX250-CDx has not yet received FDA or EMA marketing approval as of this record's date; ZIRCON is the pivotal trial underpinning that filing.

## Fields

- Kind: Trial
- Status: completed
- Last checked: 2026-09-22
- Also known as: 89Zr-girentuximab phase 3 trial
- Tags: diagnostic trial; renal cell carcinoma; immuno-PET
- Registry id: NCT03849118
- Phase: 3
- Setting: Adults with a single indeterminate renal mass (cT1, up to 7 cm) suspicious for clear cell renal cell carcinoma, scheduled for nephrectomy; a diagnostic (imaging) trial, not a treatment line
- Sponsor: Telix Pharmaceuticals
- Enrolled: 300
- Result: Met both co-primary endpoints: mean sensitivity 85.5% (95% CI 81.5-89.6) and mean specificity 87.0% (95% CI 81.0-93.1) for detecting clear cell renal cell carcinoma by 89Zr-girentuximab PET-CT against blinded central histopathology (Shuch et al., Lancet Oncology 2024)
- Outcomes: Sensitivity for ccRCC detection vs surgical histopathology: 89Zr-girentuximab PET-CT 85.5%; Specificity for ccRCC detection vs surgical histopathology: 89Zr-girentuximab PET-CT 87%

## Sources

- Lancet Oncology 2024: ZIRCON primary results (Shuch et al.): https://pubmed.ncbi.nlm.nih.gov/39270701/
- ClinicalTrials.gov: NCT03849118: https://clinicaltrials.gov/study/NCT03849118

## Connected records

- drugs: [Zirconium-89 girentuximab](https://nuclide.cc/drugs/girentuximab-zr89/)
- technologies: [CAIX PET (89Zr-girentuximab)](https://nuclide.cc/technologies/caix-pet/)
- indications: [Renal cell carcinoma](https://nuclide.cc/indications/rcc/)
- companies: [Telix Pharmaceuticals](https://nuclide.cc/companies/telix/)
- isotopes: [Zirconium-89](https://nuclide.cc/isotopes/zr-89/)

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