# CAIX PET (89Zr-girentuximab)

Source: https://onco.cc/technologies/caix-pet/  
OnCo record `caix-pet` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.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

- cancers: [Renal cell carcinoma](https://onco.cc/cancers/rcc/)
- fronts: [Imaging](https://onco.cc/fronts/imaging/)
- technologies: [Immuno-PET](https://onco.cc/technologies/immuno-pet/), [PET (positron emission tomography)](https://onco.cc/technologies/pet/)
- targets: [HIF-2α](https://onco.cc/targets/hif2a/)
- companies: [Telix Pharmaceuticals](https://onco.cc/companies/telix/)
- pathways: [VHL / HIF oxygen sensing](https://onco.cc/pathways/hif-vhl/)
- trials: [89Zr-TLX250 for PET/CT Imaging of ccRCC - ZIRCON-CP Study](https://onco.cc/trials/nct06750419/), [89Zr-TLX250 for PET/CT Imaging of ccRCC- ZIRCON Study](https://onco.cc/trials/nct03849118/), [An Investigational Scan (89Zr-DFO-GmAb PET/CT) Compared to Contrast-Enhanced CT for the Detection of Recurrent Clear Cell Renal Cell Cancer After Surgery Comparing Carbonic Anhydrase IX (CAIX) PET CT to Conventional PET CT for Post-Op Staging in Kidney Cancer](https://onco.cc/trials/nct06447103/)
- key papers: [[ 89 Zr]Zr-girentuximab for PET-CT imaging of clear-cell renal cell carcinoma: a prospective, open-label, multicentre, phase 3 trial](https://onco.cc/key-papers/paper-shuch-lancet-oncol/)
- ideas: [Biomarker-selected adjuvant therapy in RCC (ctDNA, CAIX PET, gene signatures)](https://onco.cc/ideas/idea-adjuvant-selection-rcc/), [CAIX theranostics: 89Zr-girentuximab PET and 177Lu/225Ac-girentuximab therapy](https://onco.cc/ideas/idea-caix-theranostics/)

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