Multimodal CEA-Targeted Image-Guided Colorectal Cancer Surgery using 111 In-Labeled SGM-101.

Purpose: Intraoperative image guidance may aid in clinical decision-making during surgical treatment of colorectal cancer. We developed the dual-labeled carcinoembryonic antigen-targeting tracer, [ ¹¹¹ In]In-DTPA-SGM-101, for pre- and intraoperative imaging of colorectal cancer. Subsequently, we investigated the tracer in preclinical biodistribution and multimodal image-guided surgery studies, and assessed the clinical feasibility on patient-derived colorectal cancer samples, paving the way for rapid clinical translation.
Experimental Design: SGM-101 was conjugated with p-isothiocyanatobenzyl-diethylenetriaminepentaacetic acid (DTPA) and labeled with Indium-111 ( ¹¹¹ In). The biodistribution of 3, 10, 30, and 100 μg [ ¹¹¹ In]In-DTPA-SGM-101 was assessed in a dose escalation study in BALB/c nude mice with subcutaneous LS174T human colonic tumors, followed by a study to determine the optimal timepoint for imaging. Mice with intraperitoneal LS174T tumors underwent micro-SPECT/CT imaging and fluorescence image-guided resection. In a final translational experiment, we incubated freshly resected human tumor specimens with the tracer and assessed the tumor-to-adjacent tissue ratio of both signals.
Results: The optimal protein dose of  [ ¹¹¹ In]In-DTPA-SGM-101 was 30 μg (tumor-to-blood ratio, 5.8 ± 1.1) and the optimal timepoint for imaging was 72 hours after injection (tumor-to-blood ratio, 5.1 ± 1.0). In mice with intraperitoneal tumors, [ ¹¹¹ In]In-DTPA-SGM-101 enabled preoperative SPECT/CT imaging and fluorescence image-guided resection. After incubation of human tumor samples, overall fluorescence and radiosignal intensities were higher in tumor areas compared with adjacent nontumor tissue ( P < 0.001).
Conclusions: [ ¹¹¹ In]In-DTPA-SGM-101 showed specific accumulation in colorectal tumors, and enabled micro-SPECT/CT imaging and fluorescence image-guided tumor resection. Thus, [ ¹¹¹ In]In-DTPA-SGM-101 could be a valuable tool for preoperative SPECT/CT imaging and intraoperative radio-guided localization and fluorescence image-guided resection of colorectal cancer.
(©2020 American Association for Cancer Research.)