Near-Infrared Fluorescence-Guided Segmentectomy: Added Benefit of Indocyanine Green Dye Diminishes With Surgeon Experience

Abstract

BackgroundNear-infrared fluorescence (NIF)-mapping with indocyanine green dye (ICG) facilitates the identification of the intersegmental plane during minimally invasive segmentectomy. Our pilot study showed that ICG is associated with an increase in oncological margin distance from the tumour, greater than the surgeon's best judgment. We hypothesized that, with greater experience, the surgeon's judgement will improve, and the benefit of ICG will diminish.MethodsThis is a phase 2 single-arm trial of patients undergoing robotic-assisted segmentectomy for NSCLC tumours less than 3 cm. After isolating the diseased segment(s), the predicted intersegmental plane (Dp) was identified by the thoracic surgeon. After intravenous ICG injection, the true intersegmental plane (Dt) was revealed using NIF. The primary outcome was the average distance between Dt and Dp (Dt-Dp). Comparisons were performed across 3 temporal tertiles: tertile 1 (t1) comprised of the first 30 participants, and the remaining participants were divided equally for tertiles 2 (t2) and 3 (t3). Kruskal-Wallis test was used to compare differences between tertiles (α = 0.05).ResultsA total of 190 patients were enrolled from October 2016 to June 2021. The median age was 68 (interquartile range:62-72), and 57.37%(109/190) were women. ICG injection occurred in 60.53%(115/190) of the participants, and intersegmental plane visualization was achieved in 88.70%(102/115). Dt-Dp diminished significantly across tertiles: t1 = 20.65 ± 15.82 mm, t2 = 2.42 ± 15.49 mm, and t3 = 1.36 ± 9.87 mm (P = 0.0001). Locally estimated scatterplot smoothing revealed that this distance approaches zero as the surgeon performs more cases.ConclusionIn our single-surgeon experience with robotic-assisted segmentectomy for NSCLC, the added value of NIF-mapping with ICG diminishes with surgeon experience.

Keywords: added benefit; indocyanine green dye; near-infrared fluorescence-guided; robotic-assisted segmentectomy; surgeon experience.

Graphical Abstract

Figure 1.

ICG Injection and Outcome Measurement Protocol. The primary outcome of this study was the average distance between the true plane and the predicted plane (Dt-Dp). After ligation of the vasculature, the predicted intersegmental plane (Dp) was marked with cautery by the surgeon, which is depicted as yellow dashes in Figure 1(A). After intravascular injection of indocyanine green dye, near-infrared fluorescence mapping delineates the actual intersegmental plane (Dt), depicted in red dashes in Figure 1(B), between the excluded segment (dark) and remaining lung (green). The blue arrows demonstrate the difference between the predicted plane and the true plane (Dt-Dp).

Figure 2.

Average Dt-Dp Across Tertiles. In the 45 cases in which ICG corrected the surgeon’s estimate of the intersegmental plane (score of 7/7 on the 7-item binary scale), the average Dt-Dp diminished significantly in Tertile 3 [10.00 (IQR: 6.67-10.00) mm], when compared to t1 and t2 [20.00 (IQR: 13.33-30.33) mm and 21.50 (IQR: 13.33-26.70) mm, respectively (P = 0.003)].

Figure 3.

Added Value of Indocyanine Green Dye Over Surgeon’s Case Number. A locally estimated scatterplot smoothing was performed with ICG case number as the independent variable to examine the relationship between surgeon experience with ICG and the ability to predict the location of the invisible intersegmental plane.

Figure 4.

Added Value of Indocyanine Green Dye Stratified by Segment Complexity. A locally estimated scatterplot smoothing plot stratified by segment complexity showing that the slight increase in Dt-Dp in the second tertile was mostly associated with simple, and not complex, segmentectomy.