Dr. Bowman on Rationale for Radio-Labeled Atezolizumab PET/CT Scans in RCC

I. Alex Bowman, MD, assistant professor, Division of Hematology/Oncology, Harold C. Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, discusses the rationale for an exploratory, early phase I clinical trial (NCT04006522) of radio-labeled ⁸⁹Zr-atezolizumab (Tecentriq) PET/CT scans in renal cell carcinoma (RCC).

In several cancers, it has been found that the amount of PD-L1 expression in the tumor and the tumor microenvironment correlates with response to immunotherapy; however, this has not been the case in kidney cancer, says Bowman.

Several major immunotherapy trials have examined the question of why this is. It is hypothesized that PD-L1 expression will have to be present in the tumor or the surrounding tissue in order for patients to respond to immunotherapy, so either the PD-L1 is not adequately being detected or this expression might be variable within the tumors or different metastatic sites, explains Bowman.

As such, this exploratory clinical trial aims to provide a noninvasive way to detect PD-L1 expression in 2 cohorts: patients with localized RCC who will undergo ⁸⁹Zr-atezolizumab PET/CT prior to nephrectomy and patients with metastatic RCC who will undergo ⁸⁹Zr-atezolizumab PET/CT prior to treatment with an immune checkpoint inhibitor.

Co-primary endpoints of the trial will be an exploratory analysis correlating ⁸⁹Zr-atezolizumab uptake with PD-L1 immunohistochemical analyses in patients with localized advanced disease, as well as an examination of whether ⁸⁹Zr-atezolizumab uptake across metastatic sites of kidney cancer correlates with knwon radiographically evident metastatic sites of disease, PD-L1 expression, and response to checkpoint inhibitor therapy.