Study Shows Impact of CAIX-Targeted PET Radiotracer for Renal Malignancies

A new analysis from the ZIRCON phase 3 trial of the PET/CT agent (⁸⁹Zr)girentuximab suggests that in addition to enhanced detection of clear cell renal cell carcinoma (ccRCC), the radiotracer may offer significant utility for non-RCC renal malignancies as well.

In a cohort of 300 patients, researchers assessed the use of (89Zr)girentuximab for non-clear cell renal cell carcinoma (nccRCC).

The researchers found that(⁸⁹Zr)girentuximab, a carbonic anhydrase IX (CAIX)-targeted radiotracer, provided an 82 percent sensitivity, an 87 percent specificity and a 98 percent positive predictive value (PPV) for any renal cancer.

“ … Results from our retrospective analysis support that positive [⁸⁹Zr]girentuximab PET scans may prove to be useful to predict any form of renal malignancy, regardless of histology,” noted lead study author Aboubacar Kaba, MD, who is affiliated with the UCLA Institute of Urologic Oncology and the David Geffen School of Medicine at UCLA, and colleagues.

The study authors emphasized the low renal excretion with (⁸⁹Zr)girentuximab and the agent’s predominant elimination/clearance through the hepatobiliary system as key advantages for imaging of primary renal tumors.

Noting the advanced stage and worse prognosis with papillary RCC (pRCC) and CAIX expression, the researchers pointed out that imaging with (⁸⁹Zr)girentuximab in these patients revealed a significantly higher mean SUVmax for PET avid cases in contrast to PET negative cases (16 vs. 11) as well as a higher mean CAIX score (28 vs. 22).

“The utility of this test may be important in distinguishing more hypoxic/aggressive disease from indolent tumors with clear treatment implications. This may provide an additional tool to aid in risk stratifying or guiding patient and clinician decisions in the treatment of renal masses,” added Kaba and colleagues.

(Editor’s note: For related content, see “A Closer Look at New Guidelines for Molecular Imaging of Renal Masses: An Interview with Steven Rowe, MD, Part 1,” “Study for Emerging PET/CT Agent Reveals ‘New Standard’ for Detecting Clear Cell Renal Cell Carcinoma” and “Could the PET Imaging Agent ITM-94 be a Game Changer for Detecting Clear Cell Renal Cell Carcinoma?”)