124I-cG250 PET in clear cell renal cell carcinoma (ccRCC)

Learning Objectives 124I-cG250 (REDECTANE) is a promising PET agent for ccRCC, which is currently under investigation. After viewing this Exhibit, attendees will be familiar with: 1. the proposed role of 124I-cG250 in diagnosing ccRCC in indeterminate renal masses; 2. its potential roles in predicting and monitoring response to therapy; 3. its technical properties and limitations.

An increasing number of indeterminate renal masses are detected on cross-sectional imaging, a significant number of which are benign. Therefore, an imaging test that could help to distinguish ccRCC, the most common and most aggressive subtype of RCC, from other renal tumors would be very beneficial. On the other hand, metastatic ccRCC remains a very deadly disease with a 5-year survival rate of <10%. Targeted drugs, which improve survival in metastatic ccRCC, are associated with minimal to modest size decrease on CT/MR, and have significant side effects. Therefore, an imaging test that could a priori determine which patients would benefit from these drugs and monitor their effect would be very timely. cG-250 is a chimeric antibody that recognizes carbonic anhydrase IX (CAIX), which is expressed in the cell membrane of ccRCC. 124I-cG250 has been demonstrated to distinguish ccRCC from other renal tumors. We will review the related literature with a particular emphasize on the size of an indeterminate renal mass and the difficulties that 124I-cG-250 PET could face in this regard in clinical practice. We will also discuss other technical properties of 124I and its benefits compared to 18F but also the challenges that it might pose to the clinical utilization of 124I-cG250. Among others, we will look at particular issues associated with quantification of 124I uptake on PET. Furthermore, we will look at CAIX as a tissue biomarker and predictor of response in ccRCC, and the potentials of 124I-cG250 as an imaging biomarker in predicting and monitoring response to targeted drugs.