A Phase I Clinical Trial of Targeted Intraoperative Molecular Imaging for Pulmonary Adenocarcinomas

Background: Intraoperative identification of pulmonary nodules, particularly small lesions, can be challenging. We hypothesize that folate receptor-targeted intraoperative molecular imagining can be safe and improve localization of pulmonary nodules during resection. Methods: Twenty subjects with biopsy-proven pulmonary adenocarcinomas were enrolled in a phase I clinical trial to test the safety and feasibility of OTL38, a novel folate receptor-α (FRα) targeted optical contrast agent. During resection, tumors were imaged in situ and ex vivo and fluorescence was quantified. Resected specimens were analyzed to confirm diagnosis, and immunohistochemistry was utilized to quantify FRα expression. A multivariate analysis using clinical and tumor data was performed to determine variables impacting tumor fluorescence. Results: Of the 20 subjects, three grade I adverse events were observed: all transient nausea/abdominal pain. All symptoms resolved after completing the infusion. Sixteen of 20 subjects (80%) had tumors with in situ fluorescence with a mean tumor-to-background fluorescence level of 2.9 (interquartile range, 2.1 to 4.2). The remaining 4 subjects’ tumors fluoresced ex vivo. In situ fluorescence was dependent on depth from the pleural surface. Four subcentimeter nodules not identified on preoperative imaging were detected with intraoperative imaging. Conclusions: This phase I trial provides preliminary evidence suggesting that folate receptor-targeted molecular imaging with OTL38 is safe, with tolerable grade I toxicity. These data also suggest that OTL38 accumulates in known lung cancers and may improve identification of synchronous malignancies. Our group is initiating a five-center, phase II study to better understand the clinical implications of intraoperative molecular imaging using OTL38.