Review on endobronchial therapies-current status and future

Abstract

There is a growing demand for lung parenchymal-sparing localized therapies due to the rising incidence of multifocal lung cancers and the growing number of patients who cannot undergo surgery. Lung cancer screening has led to the discovery of more pre-malignant or early-stage lung cancers, and the focus has shifted from treatment to prevention. Transbronchial therapy is an important tool in the local treatment of lung cancers, with microwave ablation showing promise based on early and mid-term results. To improve the precision and efficiency of transbronchial ablation, adjuncts such as mobile C-arm platforms, software to correct for computed tomography (CT)-to-body divergence, metal-containing nanoparticles, and robotic bronchoscopy are useful. Other forms of energy such as steam vapor therapy, pulsed electric field, and photodynamic therapy are being intensively investigated. In addition, the future of transbronchial therapies may involve the intratumoral injection of novel agents such as immunomodulating agents, gene therapies, and chimeric antigen receptor T cells. Extensive pre-clinical and some clinical research has shown the synergistic abscopal effect of combination of these agents with ablation. This article aims to provide the latest updates on these technologies and explore their most likely future applications.

Keywords: Transbronchial ablation; microwave ablation; photo dynamic therapy; pulsed electric field; robotic bronchoscopy.

Figure 1

Pre- and post-ablation cone-beam CT images of a right lower lobe nodule. Column (A) is a pre-ablation cone-beam CT in two axes showing a 7 mm right lower lobe solid colorectal lung metastasis in a patient who had undergone right upper and middle lobectomy. Column (B) shows the post-ablation CT after microwave ablation (100W × 10 minutes × 2), the lesion (yellow outline) is covered adequately by surrounding ground glass opacity which represents the ablation zone, with minimal margin of 8 mm. CT, computed tomography.

Figure 2

Images during ENB navigation using the Illumisite^TM platform. Figure (A) shows the tip of locatable guide pointing directly at the lesion (represented by green ball) after peripheral navigation. In Figure (B), the locatable guide is removed, but there are positional sensors embedded in the extended working channel, showing its tip pointing also at the lesion. In Figure (C), the cross hair is shown pointing slightly off center at the lesion which would require further manipulation to ensure target view, while the tip of catheter is shown to be 2 cm from the target lesion. ENB, electromagnetic navigation bronchoscopy.

Figure 3

This figure shows the operating room setup during Cios Spin^® mobile C-arm image acquisition.

Figure 4

During robotic bronchoscopy by Auris Monarch^TM, the left hand panel shows the real-time bronchoscopic view, middle panels show bull’s eye view with cross hair in centre and lesion represented by yellow ball, while the right hand panels show the pre-operative CT scan images in 3 perpendicular axes. CT, computed tomography.

Figure 5

Intraoperative layout during robotic bronchoscopy. Figure (A) shows the operator standing on the right side of patient manipulating the robotic bronchoscope by Auris Monarch^TM (which has been inserted through the endotracheal tube) using a controller. The screen (*) shows real time bronchoscopic view during the initial registration process. Figure (B) shows robotic bronchoscopy used together with cone-beam CT in hybrid operating room to further improve the accuracy of navigation, biopsy or treatment. A screen shows robotic navigation (*) and another screen shows real time fluoroscopy (#), while another operator advances biopsy tools through the robotic bronchoscope (@). CT, computed tomography.

Figure 6

Operative setup when performing robotic ENB microwave ablation is similar to that during robotic ENB biopsy using Auris Monarch^TM, except that the treatment catheter is connected to the microwave generator on the left. ENB, electromagnetic navigation bronchoscopy.

Figure 7

This shows the overlay of two pre-ablation CT scans with ablation catheter positioned on each side of nodule (target 2) to perform bracket ablation. The catheter was put in position 1 with ablation performed, then renavigated to position 2 to deliver a second ablation, in order to ensure adequate margin on both sides of nodule. CT, computed tomography.

Figure 8

Operative set up during transbronchial pulsed electric field ablation. The endobronchial applicator is inserted into the bronchoscope on the right side of photo, and is connected to appliances on the left side which includes the electrical signal generator, and impedance and ECG monitors. ECG, electrocardiography.