Near-infrared dyed antibodies detect renal carcinoma during surgery

The next generation of intraoperative imaging for clear-cell renal cell carcinoma (ccRCC) may incorporate near-infrared (NIR) dyed antibodies that track down a tumor biomarker, according to a study published online April 21 in the Journal of Nuclear Medicine.

NIR swatched chimeric monoclonal antibody girentuximab was used intraoperatively in this study to detect carbonic anhydrase IX (CAIX)–expressing lesions via fluorescence ccRCC imaging.

Constantijn H.J. Muselaers, from the deparment of urology at Radboud University Medical Center in Nijmege, The Netherlands, and colleagues evaluated I-125 labeled girentuximab using optical and SPECT imaging to determine their potential for intraoperative imaging. Results of the primary study showed encouraging findings. 

“[NIR] imaging probes for improved tumor characterization and delineation during surgery is increasing, although clinical applications have been limited,” wrote Muselaers et al. “The sensitivity of NIR imaging might be extremely high, and because of the low level of tissue autofluorescence in this part of the light spectrum, the use of NIR imaging probes could yield optimal visualization of tissues of interest. Unfortunately, the limited depth of penetration of the light emitted from these agents hampers whole-body applications.”

Intraoperative imaging breaks down that barrier. For this study, mice with subcutaneous CAIX-positive and CAIX-negative SK-RC-52 ccRCC tumors were injected with either I-125 labeled girentuximab-IRDye800CW or I-125 labeled girentuximab. The control group were administered I-125 labeled MOPC21-IRDye800CW. Optical and micro-SPECT scans were taken until three days following injection. Results showed proof positive of CAIX-expressing ccRCC xenografts using optical imaging and micro-SPECT imaging one day after the injection of I-125 girentuximab-IRDye800CW.

Fluorescence imaging and biodistribution tests showed high uptake of I-125 girentuximab-IRDye800CW in CAIX-positive ccRCC xenografts. Specific tumor uptake was demonstrated by minimal uptake of I-125 girentuximab-IRDye800CW in the CAIX-negative SK-RC-59 tumor. No uptake of I-125 MOPC21-IRDye800CW was found in the controls.

“Subcutaneous CAIX-expressing ccRCC xenografts were visualized by optical imaging with I-125 girentuximab-IRDye800CW,” concluded the researchers. “Optical images showed good concordance with micro-SPECT images. The accumulation of I-125 girentuximab-IRDye800CW in ccRCC tumors was high and specific. Girentuximab-IRDye800CW potentially could be used for the intraoperative detection of CAIX-expressing tumors and the assessment of residual tumor in resection margins or metastatic lesions in patients with ccRCC.”