{"id":17706,"date":"2026-05-11T05:21:15","date_gmt":"2026-05-11T08:21:15","guid":{"rendered":"https:\/\/rtmedical.com.br\/tmp-en-1778487674807\/"},"modified":"2026-05-11T05:21:24","modified_gmt":"2026-05-11T08:21:24","slug":"girentuximab-caix-pet-renal-tumors-zircon","status":"publish","type":"post","link":"https:\/\/rtmedical.com.br\/en\/girentuximab-caix-pet-renal-tumors-zircon\/","title":{"rendered":"PET Girentuximab: 98% PPV Across Renal Tumors"},"content":{"rendered":"

A new retrospective analysis of the phase 3 ZIRCON<\/strong> trial suggests that the PET\/CT radiopharmaceutical (\u2078\u2079Zr)girentuximab<\/em> can go beyond its initial indication \u2014 detecting clear-cell renal cell carcinoma (ccRCC) \u2014 and offer clinically meaningful utility in non-clear-cell renal malignancies<\/strong> as well. The numbers, released on May 5, 2026, show 82% sensitivity, 87% specificity and a positive predictive value of 98% for any renal cancer<\/strong> in a cohort of 300 patients \u2014 a tier that places the agent among the most discriminative tools ever tested for renal masses.<\/p>\n

What is girentuximab<\/h2>\n

Girentuximab is a monoclonal antibody radiolabeled with zirconium-89 (\u2078\u2079Zr), a 78.4-hour half-life isotope. It binds carbonic anhydrase IX (CAIX)<\/strong>, a membrane enzyme heavily expressed in conditions of tumor hypoxia \u2014 and especially abundant in clear-cell renal cell carcinoma, where loss of the VHL gene constitutively activates the HIF\/CAIX axis. The conjugate was originally developed to separate, on PET\/CT, characteristically “clear” renal masses from normal kidney tissue. The long half-life of zirconium allows imaging at 3 to 7 days post-injection, enough time for tissue perfusion to stabilize.<\/p>\n

\"Posterior
Posterior renal mass on contrast-enhanced CT (A) and fused PET\/CT (B) showing \u2078\u2079Zr-girentuximab uptake; H&E and CAIX staining post-resection in a 78-year-old man.<\/figcaption><\/figure>\n

Study details<\/h2>\n

The group, led by Aboubacar Kaba (UCLA Institute of Urologic Oncology \/ David Geffen School of Medicine), retrospectively reviewed 300 patients who underwent PET\/CT within the ZIRCON framework and whose tumors were not histologically ccRCC (non-clear-cell renal cell carcinoma, or nccRCC). The reads were blinded to pathology and results were cross-referenced against the surgical specimen. The reported metrics \u2014 82% sensitivity, 87% specificity and 98% PPV \u2014 are particularly striking in a context where conventional radiologists hit roughly 65-75% accuracy with contrast-enhanced CT in differentiating benign from malignant small renal masses.<\/p>\n

The authors also looked at subgroups. In papillary renal cell carcinoma (pRCC)<\/strong>, comparing PET-avid versus PET-negative cases yielded mean SUVmax of 16 versus 11<\/strong> and a mean CAIX score of 28 versus 22, suggesting correlation between tracer uptake and immunohistochemical CAIX expression in tissue. The finding matters because pRCC is considered a more aggressive disease with worse prognosis than classical ccRCC; an imaging marker that separates “cold” from “hot” pRCC could shift surgical decision-making.<\/p>\n

Why this matters clinically<\/h2>\n

The major clinical pain point in uro-oncology is the management of small renal masses with inconclusive CT. The current sequence includes gadolinium MRI, percutaneous biopsy (with a 10-15% non-diagnostic rate in small lesions) and, frequently, diagnostic partial nephrectomy. A radiotracer with 98% PPV reduces surgical false positives and opens room for active surveillance in masses the PET classifies as likely benign. For tumors with high uptake, the molecular information can redirect to targeted therapy \u2014 similar to oncologic risk stratification powered by AI platforms<\/a> in other diseases.<\/p>\n

Another technical advantage highlighted by the authors is the low renal excretion of the tracer<\/strong>. Because \u2078\u2079Zr-girentuximab is eliminated predominantly via the hepatobiliary route, background noise in the renal pelvis is minimal \u2014 improving the read precisely where the lesion of interest sits. By comparison, agents like \u00b9\u2078F-FDG and PSMA have substantial renal excretion and require hydration tricks or delayed imaging to mitigate artifacts.<\/p>\n

The regulatory and clinical landscape<\/h2>\n

ZIRCON was the phase 3 trial that supported the product’s FDA approval pathway. The retrospective extension to nccRCC strengthens the case for label broadening and likely supports additional approved indications. Companies like Telix Pharmaceuticals \u2014 the trial sponsor \u2014 are consolidating as central pieces of the so-called “radioligand therapy” wave, where diagnosis and treatment share a molecular target. In parallel, planning platforms such as GE’s MIM ComboTherapy GYN<\/a> illustrate how the radiotheranostic ecosystem is structuring itself to integrate PET, dosimetry and treatment into a single workflow.<\/p>\n

Outside the U.S., regulatory adoption is uneven. Brazil’s Anvisa has not yet registered girentuximab for clinical use, and zirconium-89 PET depends on cyclotrons able to produce or import the isotope under viable logistics \u2014 limited to a handful of centers in S\u00e3o Paulo, Rio de Janeiro, Florian\u00f3polis and Recife. The picture may shift as national centers connect with international academic networks and nuclear medicine societies include the discussion in clinical guidelines.<\/p>\n

Implications for radiology workflow<\/h2>\n

For the radiologist, the result means current “renal mass characterization” protocols are worth revisiting \u2014 and that referral for molecular PET should be considered in patients with indeterminate lesions on CT and MRI, contraindications to biopsy or bilateral tumors. Whole-body MRI strategies powered by AI<\/a> follow the same arc: reduce diagnostic biopsies through quantitative imaging biomarkers.<\/p>\n

Important caveats remain. This is a retrospective analysis with 300 patients selected against ZIRCON eligibility criteria, and prospective validation in non-ccRCC cohorts is still needed. The authors also note CAIX expression varies across histological subtypes and may be low in chromophobe or oncocytic tumors, potentially limiting performance there. Even so, the evidence package, layered on top of the phase 3 track record, is likely to consolidate \u2078\u2079Zr-girentuximab as a standard imaging tool in uro-oncology within the next two years.<\/p>\n

Source:<\/strong> Diagnostic Imaging \u2014 Study Shows Impact of CAIX-Targeted PET Radiotracer for Renal Malignancies (May 5, 2026)<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

A ZIRCON sub-analysis extends \u2078\u2079Zr-girentuximab to non-clear-cell renal tumors: 82% sensitivity, 87% specificity, 98% PPV. See the findings.<\/p>\n","protected":false},"author":1,"featured_media":17702,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"ngg_post_thumbnail":0,"fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[100,99],"tags":[],"class_list":{"0":"post-17706","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-radiology","8":"category-radiotherapy"},"aioseo_notices":[],"rt_seo":{"title":"","description":"ZIRCON sub-analysis extends \u2078\u2079Zr-girentuximab to non-clear-cell renal tumors: 82% sensitivity, 87% specificity, 98% PPV (n=300). See findings.","canonical":"","og_image":"","robots":"index,follow","schema_type":"Article","include_in_llms":true,"llms_label":"PET girentuximab in renal cancer","llms_summary":"A ZIRCON retrospective analysis shows \u2078\u2079Zr-girentuximab PET\/CT achieves 82% sensitivity, 87% specificity and 98% PPV in non-clear-cell renal tumors (n=300).","faq_items":[],"video":[],"gtin":"","mpn":"","brand":"","aggregate_rating":[]},"_links":{"self":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/17706\/"}],"collection":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/"}],"about":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/types\/post\/"}],"author":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/users\/1\/"}],"replies":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/comments\/?post=17706"}],"version-history":[{"count":1,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/17706\/revisions\/"}],"predecessor-version":[{"id":17708,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/posts\/17706\/revisions\/17708\/"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/17702\/"}],"wp:attachment":[{"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/media\/?parent=17706"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/categories\/?post=17706"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rtmedical.com.br\/en\/wp-json\/wp\/v2\/tags\/?post=17706"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}