Near-infrared intraoperative imaging for minimally invasive pulmonary metastasectomy for sarcomas

Abstract

Background: Complete pulmonary metastasectomy for sarcoma metastases provides patients an opportunity for long-term survival and possible cure. Intraoperative localization of preoperatively identified metastases and identification of occult lesions can be challenging. In this trial, we evaluated the efficacy of near-infrared (NIR) intraoperative imaging using second window indocyanine green during metastasectomy to identify known metastases and to detect occult nodules.

Methods: Thirty patients with pulmonary nodules suspicious for sarcoma metastases were enrolled in an open-label, feasibility study (NCT02280954). All patients received intravenous indocyanine green (5 mg/kg) 24 hours before metastasectomy. Patients 1 through 10 (cohort 1) underwent metastasectomy via thoracotomy to assess fluorescence patterns of nodules detected by traditional methods (preoperative imaging and intraoperative visualization/bimanual palpation). After confirming reliability within cohort 1, patients 11 through 30 (cohort 2) underwent video-assisted thoracic surgery metastasectomy with NIR imaging.

Results: In cohort 1, 14 out of 16 preoperatively identified pulmonary metastases (87.5%) displayed tumor fluorescence. Nonfluorescent metastases were deeper than fluorescent metastases (2.1 cm vs 1.3 cm; P = .03). Five out of 5 metastases identified during thoracotomy displayed fluorescence. NIR imaging identified 3 additional occult lesions in this cohort. In cohort 2, 33 out of 37 known pulmonary metastases (89.1%) displayed fluorescence. Nonfluorescent tumors were deeper than 2.0 cm (P = .007). NIR imaging identified 24 additional occult lesions. Of 24 occult lesions, 21 (87.5%) were confirmed metastases and the remaining 3 nodules were lymphoid aggregates.

Conclusions: NIR intraoperative imaging with indocyanine green (5 mg/kg and 24 hours before surgery) localizes known sarcoma pulmonary metastases and identifies otherwise occult lesions. This approach may be a useful intraoperative adjunct to improve metastasectomy.

Keywords: ICG; intraoperative imaging; metastasectomy; optical imaging; sarcoma.

Conflict of interest statement

Conflicts of Interest: None

Copyright © 2018 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1:. Representative example of NIR intraoperative imaging during thoracotomy for subject with osteosarcoma metastases.

(a,b) Preoperative high-resolution CT revealing multiple right-sided pulmonary metastases. (c) Traditional brightfield view of known basilar metastasis, (d) Near-infrared merged view of known basilar metastasis. (e) Bright field view of right middle lobe revealing no obvious disease. (f) Near-infrared merged view demonstrating several occult metastases measuring 3-5mm. red circle-metastasis

Figure 2:. Summary of Metastases Identified within Cohort 1.

Within the 10 subjects enrolled in Cohort 1, a total 24 metastases were identified using a combination of preoperative CT, intraoperative palpation, and NIR imaging. Sixteen lesions were identified by preoperative CT, with 14 being fluorescent. Five lesions were identified by bimanual palpation, and each was fluorescent. Three additional lesions were identified by NIR imaging alone.

Figure 3:. Representative examples of NIR intraoperative imaging during VATS metastasectomy

Left Column—preoperative high-resolution CT; Middle column—Bright field (Traditional Views); Right column—NIR merged view.

Figure 4:. Summary of Metastases Identified within Cohort 2.

Among the 20 subjects enrolled in Cohort 2, 58 metastases were identified using a combination of preoperative CT and intraoperative NIR imaging. Thirty-three of 37 lesions identified by preoperative CT were fluorescent. NIR imaging identified 24 additional lesions during VATS, 21 were histologically confirmed metastases.