In ccRCC, a potential tumor target is CAIX, which is overexpressed in more than 90% of ccRCC tumors and has been shown to play a role in disease progression.75,76 177Lu-labeled anti-CA-IX antibodies (177Lu-girentuximab) was previously investigated in a phase 2 study that comprised 14 patients with metastatic ccRCC.77 Among the 14 enrolled patients, 8 patients had stable disease and 1 patient achieved a PR after the first cycle. The gene discussed is CA9; the disease is nonpapillary renal cell carcinoma.