Using Immuno-PET to Detect PD-L1 in Renal Cell Carcinoma: Case Report
Posted: Wednesday, August 7, 2019
Researchers used immuno–positron-emission tomography (immunoPET) to detect PD-L1 in renal cell carcinoma, according to a case report published in the Journal for ImmunoTherapy of Cancer by James Brugarolas, MD, PhD, of The University of Texas Southwestern Medical Center, and colleagues. The carcinoma was a male patient’s tumor grafted into mice. Perhaps if further clinically evaluated and developed, this type of test could be used to predict which patients will respond to PD-L1–targeted immunotherapy.
“To our knowledge, this is the first report of noninvasive detection of PD-L1 in renal cancer using molecular imaging,” the investigators wrote.
The patient, a 49-year-old man, had a tumor in his right kidney and adrenal gland that was metastatic to his lungs and one rib. He underwent a cytoreductive nephrectomy. Histology showed a grade 4 clear cell renal cell carcinoma with extensive sarcomatoid features.
The investigators implanted samples from his tumor into mice, which grew renal tumors by 18 days later. The researchers then labeled atezolizumab with radioactive zirconium-89 and injected it into the mice. Because atezolizumab binds to PD-L1, they could then use PET scans to identify whether the tumors in the mice were PD-L1–postitive.
The mice with the patient’s tumor displayed higher levels of labeled atezolizumab than control mice with implanted PD-L1–negative tumors. This finding matched earlier results that PD-L1 was expressed in more than 30% of the patient’s tumor cells. The pathologist who scored the PET scans was blinded to the earlier results.
According to the investigators, detection of PD-L1 was clinically relevant: The patient’s disease progressed quickly when treated with high-dose interleukin-2 and then pazopanib, but he showed a durable response and regression of lung metastases when switched to the PD-1 blocker nivolumab. At the time of the report, the patient had been off nivolumab for 7 months with no disease progression.
Disclosure: The study authors reported no conflicts of interest.