Complete resection of
tumor lesions in advanced stage
ovarian cancer patients is of utmost importance, since the extent of residual disease after surgery strongly affects survival. Intraoperative imaging may be useful to improve surgery in these patients.
Farletuzumab is a humanized
IgG1 antibody that specifically recognizes the
folate receptor alpha (FRα). Labeled with a radiolabel and a
fluorescent dye,
farletuzumab may be used for the intraoperative detection of
ovarian cancer lesions. The current aim is to demonstrate the feasibility of FRα-targeted dual-modality imaging using 111In-farletuzumab-IRDye800CW in an intraperitoneal
ovarian cancer model. Biodistribution studies were performed 3 days after injection of 3, 10, 30, or 100 μg of 111In-farletuzumab-IRDye800CW in mice with subcutaneous IGROV-1
tumors (5 mice per group). In mice with intraperitoneal IGROV-1
tumors the nonspecific uptake of 111In-farletuzumab-IRDye800CW was determined by coinjecting an excess of unlabeled
farletuzumab. MicroSPECT/CT and fluorescence imaging were performed 3 days after injection of 10 μg of 111In-farletuzumab-IRDye800CW. FRα expression in
tumors was determined immunohistochemically. Optimal
tumor-to-blood-ratios (3.4-3.7) were obtained at
protein doses up to 30 μg. Multiple intra-abdominal
tumor lesions were clearly visualized by microSPECT/CT, while uptake in normal tissues was limited. Fluorescence imaging was used to visualize and guide resection of superficial
tumors. Coinjection of an excess of unlabeled
farletuzumab significantly decreased
tumor uptake of 111In-farletuzumab-IRDye800CW (69.4 ± 27.6 versus 18.3 ± 2.2% ID/g, p < 0.05). Immunohistochemical analyses demonstrated that the radioactive and fluorescent signal corresponded with FRα-expressing
tumor lesions. FRα-targeted SPECT/fluorescence imaging using 111In-farletuzumab-IRDye800CW can be used to detect
ovarian cancer in vivo and could be a valuable tool for enhanced intraoperative
tumor visualization in patients with intraperitoneal
metastases of
ovarian cancer.