# CAIX PET (89Zr-girentuximab)

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

## TL;DR

CAIX PET is a scan using an antibody against a protein almost unique to clear-cell kidney cancer, to tell cancer from benign kidney lumps without a biopsy.

## Summary

CAIX PET uses 89Zr-labelled girentuximab, an antibody against carbonic anhydrase IX, a HIF target expressed in more than 95% of clear-cell renal cell carcinomas because of VHL loss. Imaging 5 days after injection shows whether an indeterminate renal mass is clear-cell cancer without a biopsy. In the ZIRCON phase 3 (2023) it achieved sensitivity 86% and specificity 87%, giving histology-level specificity and whole-body staging in one scan. Telix's TLX250-CDx received an FDA complete response letter in 2025 over manufacturing, and resubmission is planned, so it is not yet approved; the five-day imaging delay and the 89Zr dose are practical limitations. The same antibody labelled with 177Lu is being tested therapeutically in the STARLITE trials, making CAIX a theranostic pair. It tells cancer from a benign kidney lump by lighting up a protein almost unique to clear-cell kidney cancer.

## Fields

- Kind: Technology
- Status: phase-3
- Last checked: 2026-09-07
- Principle: 89Zr-labelled anti-CAIX antibody girentuximab imaged 5 days after injection; CAIX is a HIF target expressed in >95% of clear-cell RCC via VHL loss.
- Strengths: Non-invasive histology-level specificity; Whole-body staging of clear-cell disease
- Limitations: Five-day imaging delay; 89Zr dose; Not yet approved (CRL 2025)

## Sources

- Shuch et al., ZIRCON: 89Zr-girentuximab PET-CT imaging of clear-cell renal cell carcinoma (Lancet Oncology 2024): https://doi.org/10.1016/S1470-2045(24)00402-9

## Connected records

- isotopes: [Lutetium-177](https://nuclide.cc/isotopes/lu-177/), [Zirconium-89](https://nuclide.cc/isotopes/zr-89/)
- indications: [Renal cell carcinoma](https://nuclide.cc/indications/rcc/)
- technologies: [Immuno-PET](https://nuclide.cc/technologies/immuno-pet/), [PET (positron emission tomography)](https://nuclide.cc/technologies/pet/)
- companies: [Telix Pharmaceuticals](https://nuclide.cc/companies/telix/)
- pathways: [VHL / HIF oxygen sensing](https://nuclide.cc/pathways/hif-vhl/)
- ideas: [CAIX theranostics: 89Zr-girentuximab PET and 177Lu/225Ac-girentuximab therapy](https://nuclide.cc/ideas/idea-caix-theranostics/)
- opportunities: [CAIX imaging of the indeterminate renal mass](https://nuclide.cc/opportunities/opp-caix-indeterminate-renal-mass/)
- fronts: [Molecular imaging](https://nuclide.cc/fronts/f-molecular-imaging/)
- key papers: [ZIRCON: [89Zr]Zr-girentuximab PET-CT for detecting clear-cell renal cell carcinoma](https://nuclide.cc/key-papers/paper-zircon-lancet-oncol-2024/)
- targets: [CAIX (carbonic anhydrase IX)](https://nuclide.cc/targets/caix/)
- trials: [ZIRCON](https://nuclide.cc/trials/zircon/)

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