Intraoperative near-infrared fluorescence imaging targeting folate receptors identifies lung cancer in a large-animal model

Abstract

Background: Complete tumor resection is the most important predictor of patient survival with non-small cell lung cancer. Methods for intraoperative margin assessment after lung cancer excision are lacking. This study evaluated near-infrared (NIR) intraoperative imaging with a folate-targeted molecular contrast agent (OTL0038) for the localization of primary lung adenocarcinomas, lymph node sampling, and margin assessment.

Methods: Ten dogs with lung cancer underwent either video-assisted thoracoscopic surgery or open thoracotomy and tumor excision after an intravenous injection of OTL0038. Lungs were imaged with an NIR imaging device both in vivo and ex vivo. The wound bed was re-imaged for retained fluorescence suspicious for positive tumor margins. The tumor signal-to-background ratio (SBR) was measured in all cases. Next, 3 human patients were enrolled in a proof-of-principle study. Tumor fluorescence was measured both in situ and ex vivo.

Results: All canine tumors fluoresced in situ (mean Fluoptics SBR, 5.2 [range, 2.7-8.1]; mean Karl Storz SBR 1.9 [range, 1.4-2.6]). In addition, the fluorescence was consistent with tumor margins on pathology. Three positive lymph nodes were discovered with NIR imaging. Also, a positive retained tumor margin was discovered upon NIR imaging of the wound bed. Human pulmonary adenocarcinomas were also fluorescent both in situ and ex vivo (mean SBR, > 2.0).

Conclusions: NIR imaging can identify lung cancer in a large-animal model. In addition, NIR imaging can discriminate lymph nodes harboring cancer cells and also bring attention to a positive tumor margin. In humans, pulmonary adenocarcinomas fluoresce after the injection of the targeted contrast agent. Cancer 2017;123:1051-60. © 2016 American Cancer Society.

Keywords: imaging; intraoperative; lung cancer; molecular; near-infrared.

Figure 1

A.) Preoperative CT scan showing an 8 cm right-sided pulmonary adenocarcinoma (red arrow). First the surgeon used B.) white light imaging in vivo. Next C.) the tumor is fluorescent in vivo with a SBR of 4.6 using the fluoptics and D.) was reimaged using the Karl Storz NIR camera confirming fluorescence. E.) H&E shows pulmonary adenocarcinoma and F.) IHC demonstrates 3+ FR staining. Next, graphic representation of the mean tumor and background fluorescence of tumors imaged using the G.) Karl Storz and H.) Fuloroptics NIR imaging is shown.

Figure 2

A.) A preoperative CT scan showing a right-sided 5 cm lung tumor (red arrow). B.) A traditional white light ex vivo imaging of the specimen on the backtable. Yellow circles denote clock face and locations of both tumor margin and background fluorescence measurements. C.) NIR fluorescence image using the Karl Storz device. The tumor is circumscribed and brightly fluorescent with a mean SBR of 2.7. Note there was no available quantification of background fluorescence at 12 and 3 o’clock due to lack of surrounding normal lung. D.) Folate receptor IHC with 3+ FR tumor staining. E.) Fluorescence intensity decreases as distance from the tumor boarder increases. These measurements were obtained from tumors measured with the Karl Storz imaging system. The black bars represent tumor fluorescence directly at the tumor margin and the grey and white bars represent tumor fluorescence from the background (5 mm and 10 mm from the tumor edge, respectively).

Figure 3

Example images of ex vivo white light, ex vivo NIR, and FR IHC staining of a A.) cancer containing lymph node and B.) disease free lymph node.

Figure 4

Although not evident on traditional A.) white light imaging or palpation, one canine showed evidence of retained tumor cells using B.) NIR imaging of the wound bed following tumor excision. C.) Final pathology confirmed a positive margin at the bronchus.

Figure 5

Patient DR is a 55-year-old female with a mass in her left lower lobe noted on A.) preoperative CT scan which was confirmed pulmonary adenocarcinoma preoperatively. Images obtained intraoperatively include an B.) in vivo white light image, C.) NIR fluorescence image using the Karl Storz thoracoscopic system. Pathology confirmed D.) invasive adenocarcinoma on H&E. E.) IHC confirmed strong folate receptor staining.