Bronchoscopic Ablative Therapies for Malignant Central Airway Obstruction and Peripheral Lung Tumors

Novel diagnostic processes and challenges in bronchoscopy

Diagnostic bronchoscopy is a minimally invasive procedure that plays a crucial role in the diagnosis and management of various respiratory conditions. This paper explores the advancements in technology that have revolutionized the field and focuses on the new diagnostic procedures in bronchoscopy that have emerged in recent years. These innovative techniques have expanded the diagnostic capabilities of bronchoscopy, allowing for more accurate and comprehensive evaluation of respiratory conditions. This paper will also discuss the challenges in the diagnostic process with bronchoscope.

Current diagnosis and treatment of salivary gland-type tumors of the lung

Salivary gland-type tumors of the lung are thought to originate from the submucosal exocrine glands of the large airways. Due to their rare occurrence, reports of their study are limited to small-scale or case reports. Therefore, daily clinical practices often require a search for previous reports. In the last 20 years, several genetic rearrangements have been identified, such as MYB::NF1B rearrangements in adenoid cystic carcinoma, CRTC1::MAML2 rearrangements in mucoepidermoid carcinoma, EWSR1::ATF1 rearrangements in hyalinizing clear cell carcinoma and rearrangements of the EWSR1 locus or FUS (TLS) locus in myoepithelioma and myoepithelial carcinoma. These molecular alterations have been useful in diagnosing these tumors, although they have not yet been linked to molecularly targeted therapies. The morphologic, immunophenotypic, and molecular characteristics of these tumors are similar to those of their counterparts of extrapulmonary origin, so clinical and radiologic differential diagnosis is required to distinguish between primary and metastatic disease of other primary sites. However, these molecular alterations can be useful in differentiating them from other primary lung cancer histologic types. The management of these tumors requires broad knowledge of the latest diagnostics, surgery, radiotherapy, bronchoscopic interventions, chemotherapy, immunotherapy as well as therapeutic agents in development, including molecularly targeted agents. This review provides a comprehensive overview of the current diagnosis and treatment of pulmonary salivary gland tumors, with a focus on adenoid cystic carcinoma and mucoepidermoid carcinoma, which are the two most common subtypes.

Bronchoscopic Laser Resection as a Monotherapy for Bronchial Carcinoid

Lung carcinoid tumors are rare neuroendocrine cancers that primarily affect younger individuals and exhibit unique epidemiological characteristics unrelated to smoking or environmental factors. Symptoms may include coughing and wheezing. Bronchoscopic biopsy is the standard for diagnosis, with surgical resection as the gold standard treatment. Recent advances, such as laser resection, offer alternative options. We present a case of a 46-year-old female with bronchial carcinoid successfully treated using bronchoscopic diode laser therapy, highlighting its minimally invasive benefits. The success of this approach depends on tumor location, underscoring the importance of considering tumor characteristics in treatment decisions. Our report contributes to the evolving landscape of bronchogenic tumor management, emphasizing the need for continued research.

Anesthetic considerations in interventional pulmonology

PURPOSE OF REVIEW

In this review, we highlight the important anesthetic consideration that relate to interventional bronchoscopic procedures for the management of central airway obstruction due to anterior mediastinal masses, endoluminal endobronchial obstruction, peripheral bronchoscopy for diagnosis and treatment of lung nodules, bronchoscopic lung volume reduction and medical pleuroscopy for diagnosis and management of pleural diseases.

RECENT FINDINGS

The advent of the field of Interventional Pulmonology has allowed for minimally invasive options for patients with a wide range of lung diseases which at times have replaced more invasive surgical procedures. Ongoing research has shed light on advancement in anesthetic techniques and management strategies that have increased the safety during peri-operative management during these complex procedures. Current evidence focusing on the anesthetic techniques is presented here.

SUMMARY

The field of Interventional Pulmonology requires a tailored anesthetic approach. Recent advancements and ongoing research have focused on expanding the partnership between the anesthesiologist and interventional pulmonologists which has led to improved outcomes for patients undergoing these procedures.

Temperature-controlled laser thermal therapy system using a newly developed laparoscopic system equipped with an ultra-compact thermographic camera

Laser thermal therapy is one of the treatments for malignant tumors. We developed a thermal endoscope using an ultra-compact thermo-sensor and established a new laparoscopic laser thermal therapy system to heat cancer tissue at an appropriate temperature, focusing on the fact that thermographic cameras are capable of two-dimensional temperature mapping. Hepatocellular carcinoma (N1S1) cells were implanted into the livers of Sprague-Dawley rats (n = 13) to create orthotopic hepatocellular carcinoma. Six of the rats underwent laparoscopic laser thermotherapy (70 °C, 5 min) using the newly developed system, and the others underwent laparoscopic insertion only. Lesion volume measurement and histological evaluation were performed in all of the rats. The laparoscopic laser thermal therapy system provided stable temperature control. When a temperature of 70 °C was used for the set temperature, the temperature of the target cancer was maintained within the range of 68-72 °C for 93.2% of the irradiation time (5 min). The median volume of the tumors that were thermally treated was significantly smaller than that of the untreated tumors. The newly developed laparoscopic laser thermal therapy system was capable of maintaining the temperature of the tumor surface at any desired temperature and was proven to be effective in treatment of the rat hepatocellular carcinoma model.

Therapeutic bronchoscopy followed by sequential radiochemotherapy in the management of life-threatening tracheal adenoid cystic carcinoma: a case report

Background

Adenoid cystic carcinoma of the lung is a distinctive salivary-gland-type malignant epithelial neoplasm that rarely presents as a primary tumor of the respiratory tract. Complete surgical resection remains the treatment of choice for adenoid cystic carcinoma. We present a case of large ACC tumors that caused severe central airway obstruction and were effectively treated with therapeutic bronchoscopy followed by radiotherapy and chemotherapy.

Case presentation

A 31-year-old Malay Indonesian female patient who was a nonsmoker and had no family history of cancer was admitted to the emergency ward because of worsening breathlessness accompanied by stridor since 1 week prior. Chest computed tomography revealed segmental atelectasis of the left lung; a mass on the left main bronchus, with infiltrates in segments 1, 2, and 3 of the left lung; and consolidation in the left inferior lobe, with narrowing of the main left bronchus. Lobulated masses obstructing almost the entire distal trachea up to the carina and the entire left main bronchus were found on bronchoscopy. Owing to the large tumors causing severe central airway obstruction, the medical team decided to perform central airway mass removal through rigid bronchoscopy. A neodymium-doped yttrium-aluminum-garnet laser was used first to facilitate mass shrinkage. After the laser treatment, mechanical mass removal using a rigid scope was performed. The tracheal and carinal lumens were opened to > 50% of their diameter, with the left main bronchus lumen opened only slightly. After the treatment, the patient was stable, and no stridor was found. Adjuvant intensity-modulated radiotherapy and chemotherapy were performed after the therapeutic bronchoscopy. At the end of the entire treatment, reevaluation by thoracic computed tomography scan and bronchoscopy revealed no remaining mass.

Conclusions

In cases of nonresectable large adenoid cystic carcinoma tumors with life-threatening central airway obstruction, therapeutic bronchoscopy followed by sequential radiochemotherapy might achieve a complete response outcome.

Malignant Central Airway Obstruction: What's New?

Malignant central airway obstruction (MCAO) is a debilitating and life-limiting complication that occurs in an unfortunately large number of individuals with advanced intrathoracic cancer. Although the management of MCAO is multimodal and interdisciplinary, the task of providing patients with prompt palliation falls increasingly on the shoulders of interventional pulmonologists. While a variety of tools and techniques are available for the management of malignant obstructive lesions, advancements and evolution in this therapeutic venue have been somewhat sluggish and limited when compared with other branches of interventional pulmonary medicine (e.g., the early diagnosis of peripheral lung nodules). Indeed, one pragmatic, albeit somewhat uncharitable, reading of this article's title might suggest a wry smile and shug of the shoulders as to imply that relatively little has changed in recent years. That said, the spectrum of interventions for MCAO continues to expand, even if at a less impressive clip. Herein, we present on MCAO and its endoscopic and nonendoscopic management-that which is old, that which is new, and that which is still on the horizon.

Endoscopic Applications of Near-Infrared Photoimmunotherapy (NIR-PIT) in Cancers of the Digestive and Respiratory Tracts

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and promising therapy that specifically destroys target cells by irradiating antibody-photo-absorber conjugates (APCs) with NIR light. APCs bind to target molecules on the cell surface, and when exposed to NIR light, cause disruption of the cell membrane due to the ligand release reaction and dye aggregation. This leads to rapid cell swelling, blebbing, and rupture, which leads to immunogenic cell death (ICD). ICD activates host antitumor immunity, which assists in killing still viable cancer cells in the treated lesion but is also capable of producing responses in untreated lesions. In September 2020, an APC and laser system were conditionally approved for clinical use in unresectable advanced head and neck cancer in Japan, and are now routine in appropriate patients. However, most tumors have been relatively accessible in the oral cavity or neck. Endoscopes offer the opportunity to deliver light deeper within hollow organs of the body. In recent years, the application of endoscopic therapy as an alternative to surgery for the treatment of cancer has expanded, providing significant benefits to inoperable patients. In this review, we will discuss the potential applications of endoscopic NIR-PIT, especially in thoracic and gastrointestinal cancers.

Towards catheter steering using magnetic tractor beam coupling

Catheters are used in various clinical applications, and the ability to direct the catheter to the desired location is critical for clinical outcomes. Steerable catheters assist clinicians to access targeted areas, notably the vascular bundles and major vessels, while causing no damage to the surrounding tissue. A novel catheter actuation technology for catheter steering is presented in this study. The technique is simple and relies on three magnetic couples interacting with one another to generate steering motions. A proof-of-concept catheter prototype demonstrated the capacity to remotely steer a catheter over 100 mm of distance and ±45° of angular positioning, showing the potential manoeuvrability for clinical applications. It is feasible to steer a catheter using this three-magnet pair approach with the great potential to be used for catheterisation procedures. The presented mechanism's kinematics and a near-form solution for catheter steering regardless of design factors will be studied in the future.

Imaging of therapeutic airway interventions in thoracic oncology

Tracheobronchial obstruction, haemoptysis, and airway fistulas caused by airway involvement by primary or metastatic malignancies may result in dyspnoea, wheezing, stridor, hypoxaemia, and obstructive atelectasis or pneumonia, and can lead to life-threatening respiratory failure if untreated. Complex minimally invasive endobronchial interventions are being used increasingly to treat cancer patients with tracheobronchial conditions with curative or, most often, palliative intent, to improve symptoms and quality of life. The selection of the appropriate treatment strategy depends on multiple factors, including tumour characteristics, whether the lesion is predominately endobronchial, shows extrinsic compression, or a combination of both, the patient's clinical status, the urgency of the clinical scenario, physician expertise, and availability of tools. Pre-procedure multidetector computed tomography (MDCT) imaging can aid in the most appropriate selection of bronchoscopic treatment. Follow-up imaging is invaluable for the early recognition and management of any potential complication. This article reviews the most commonly used endobronchial procedures in the oncological setting and illustrates the role of MDCT in planning, assisting, and follow-up of endobronchial therapeutic procedures.

Advances in Diagnostic Bronchoscopy

The increase in incidental discovery of pulmonary nodules has led to more urgent requirement of tissue diagnosis. The peripheral pulmonary nodules are especially challenging for clinicians. There are various modalities for diagnosis and tissue sampling of pulmonary lesions, but most of these modalities have their own limitations. This has led to the development of many advanced technical modalities, which have empowered pulmonologists to reach the periphery of the lung safely and effectively. These techniques include thin/ultrathin bronchoscopes, radial probe endobronchial ultrasound (RP-EBUS), and navigation bronchoscopy—including virtual navigation bronchoscopy (VNB) and electromagnetic navigation bronchoscopy (ENB). Recently, newer technologies—including robotic-assisted bronchoscopy (RAB), cone-beam CT (CBCT), and augmented fluoroscopy (AF)—have been introduced to aid in the navigation to peripheral pulmonary nodules. Technological advances will also enable more precise tissue sampling of smaller peripheral lung nodules for local ablative and other therapies of peripheral lung cancers in the future. However, we still need to overcome the CT-to-body divergence, among other limitations. In this review, our aim is to summarize the recent advances in diagnostic bronchoscopy technology.

Therapeutic bronchoscopy facilitates liberation from mechanical ventilation and improves quality of life for critically ill patients with central airway obstruction

Central airway obstruction (CAO) remains a challenging disease for both patients who are suffering from it and for physicians who are managing it. Patients will frequently present with acute symptoms of respiratory failure that require management in an intensive care unit (ICU). While the true prevalence and incidence of CAO in the ICU setting is unknown, recent estimates suggest that approximately 20-30% of patients with a cancer diagnosis may present with CAO or develop it after diagnosis. Therapeutic bronchoscopy focuses on performing minimally invasive procedures using multiple ablative modalities to recanalize the central airway and alleviate the obstruction. While procedures are usually technically successful, they appear to be underutilized. An individually tailored approach is often used based on patient characteristics, operator preference, and available equipment. After therapeutic bronchoscopy procedures are completed, many patients are successfully liberated from mechanical ventilation (MV) or immediately transferred out of the ICU. Data reviewing the effects of therapeutic bronchoscopy have also shown success in palliation of symptoms, with significant improvement in subjective measures such as patient quality of life and dyspnea and objective values like pulmonary function studies. Given the potential benefits with a low risk profile and high likelihood of technical success, treatment of CAOs with therapeutic bronchoscopy represents a reasonable consideration for patients with acute respiratory failure in the ICU.

Alternative methods for local ablation-interventional pulmonology: a narrative review

OBJECTIVE

To discuss and summarise the background and recent advances in the approach to bronchoscopic ablative therapies for lung cancer, focusing on focal parenchymal lesions.

BACKGROUND

This series focusses on the challenges highlighted by increasing recognition of the prognostically more favourable oligometastatic disease rather than the more frequent, but prognostically poor, high tumour burden metastatic disease. While surgery, stereotactic body radiation therapy (SBRT), and trans-thoracic percutaneous ablative techniques such as microwave (MWA) and radiofrequency ablation (RFA) are well recognised options for selected cases of pulmonary oligometastasis, bronchoscopic approaches to pulmonary tumour ablation are becoming realistic alternatives. An underlying tenet driving research and implementation in this domain is that percutaneous ablative techniques are obliged to traverse the pleura leading to a high rate of pneumothorax, and risks also goes up for peri-vascular lesions. Historically low yield bronchoscopic targeting of isolated peripheral tumors have significantly improved by incorporating multi-modality high resolution imaging and processing, including navigation planning and real-time image guidances (ultrasound, electromagnetic navigation, cone-beam CT). Combining advanced image guidance with ablative technology adaptations for bronchoscopic delivery opens up the options for high dose local ablative therapies that may reduce transthoracic complications and provide palliative to curative options for limited stage primary and oligometastatic diseases.

METHODS

We conduct a narrative review of the literature summarizing the history of bronchoscopic tumor ablation approaches, technical details including biologic rational for their uses, and current evidence for each modality, as well as investigations into future applications. Because of the relative paucity of prospective studies, we have been very inclusive in our inclusion of experiences from the published clinical databases.

CONCLUSIONS

Whilst surgical resection and SBRT remain the current mainstay of curative therapies for peripheral cancers, in the foreseeable future, developments and further research will see bronchoscopic ablative therapies become viable lung sparing alternatives in those deemed suitable. The future is bright.

Microwave ablation of lung tumors: A probabilistic approach for simulation-based treatment planning

PURPOSE

Microwave ablation (MWA) is a clinically established modality for treatment of lung tumors. A challenge with existing application of MWA, however, is local tumor progression, potentially due to failure to establish an adequate treatment margin. This study presents a robust simulation-based treatment planning methodology to assist operators in comparatively assessing thermal profiles and likelihood of achieving a specified minimum margin as a function of candidate applied energy parameters.

METHODS

We employed a biophysical simulation-based probabilistic treatment planning methodology to evaluate the likelihood of achieving a specified minimum margin for candidate treatment parameters (i.e., applied power and ablation duration for a given applicator position within a tumor). A set of simulations with varying tissue properties was evaluated for each considered combination of power and ablation duration, and for four different scenarios of contrast in tissue biophysical properties between tumor and normal lung. A treatment planning graph was then assembled, where distributions of achieved minimum ablation zone margins and collateral damage volumes can be assessed for candidate applied power and treatment duration combinations. For each chosen power and time combination, the operator can also visualize the histogram of ablation zone boundaries overlaid on the tumor and target volumes. We assembled treatment planning graphs for generic 1, 2, and 2.5 cm diameter spherically shaped tumors and also illustrated the impact of tissue heterogeneity on delivered treatment plans and resulting ablation histograms. Finally, we illustrated the treatment planning methodology on two example patient-specific cases of tumors with irregular shapes.

RESULTS

The assembled treatment planning graphs indicate that 30 W, 6 min ablations achieve a 5-mm minimum margin across all simulated cases for 1-cm diameter spherical tumors, and 70 W, 10 min ablations achieve a 3-mm minimum margin across 90% of simulations for a 2.5-cm diameter spherical tumor. Different scenarios of tissue heterogeneity between tumor and lung tissue revealed 2 min overall difference in ablation duration, in order to reliably achieve a 4-mm minimum margin or larger each time for 2-cm diameter spherical tumor.

CONCLUSIONS

An approach for simulation-based treatment planning for microwave ablation of lung tumors is illustrated to account for the impact of specific geometry of the treatment site, tissue property uncertainty, and heterogeneity between the tumor and normal lung.

Bioengineering a Light-Responsive Encapsulin Nanoreactor: A Potential Tool for In Vitro Photodynamic Therapy

Encapsulins, a prokaryotic class of self-assembling protein nanocompartments, are being re-engineered to serve as "nanoreactors" for the augmentation or creation of key biochemical reactions. However, approaches that allow encapsulin nanoreactors to be functionally activated with spatial and temporal precision are lacking. We report the construction of a light-responsive encapsulin nanoreactor for "on demand" production of reactive oxygen species (ROS). Herein, encapsulins were loaded with the fluorescent flavoprotein mini-singlet oxygen generator (miniSOG), a biological photosensitizer that is activated by blue light to generate ROS, primarily singlet oxygen (¹O₂). We established that the nanocompartments stably encased miniSOG and in response to blue light were able to mediate the photoconversion of molecular oxygen into ROS. Using an in vitro model of lung cancer, we showed that ROS generated by the nanoreactor triggered photosensitized oxidation reactions which exerted a toxic effect on tumor cells, suggesting utility in photodynamic therapy. This encapsulin nanoreactor thus represents a platform for the light-controlled initiation and/or modulation of ROS-driven processes in biomedicine and biotechnology.

Interventional Pulmonology: Diagnostic and Therapeutic Advances in Bronchoscopy

BACKGROUND

Interventional pulmonology is a rapidly evolving subspecialty of pulmonary medicine that offers advanced consultative and procedural services to patients with airway diseases, pleural diseases, as well as in the diagnosis and management of patients with thoracic malignancy.

AREAS OF UNCERTAINTY

The institution of lung cancer screening modalities as well as the search of additional minimally invasive diagnostic and treatment modalities for lung cancer and other chronic lung diseases has led to an increased focus on the field of interventional pulmonology. Rapid advancements in the field over the last 2 decades has led to development of various new minimally invasive bronchoscopic approaches and techniques for patients with cancer as well as for patients with chronic lung diseases.

DATA SOURCES

A review of literature was performed using PubMed database to identify all articles published up till October 2020 relevant to the field of interventional pulmonology and bronchoscopy. The reference list of each article was searched to look for additional articles, and all relevant articles were included in the article.

THERAPEUTIC ADVANCES

Newer technologies are now available such navigation platforms to diagnose and possibly treat peripheral pulmonary nodules, endobronchial ultrasound in diagnosis of mediastinal and hilar adenopathy as well as cryobiopsy in the diagnosis of diffuse lung diseases. In addition, flexible and rigid bronchoscopy continues to provide new and expanding ability to manage patients with benign and malignant central airway obstruction. Interventions are also available for diseases such as asthma, chronic bronchitis, chronic obstructive pulmonary disease, and emphysema that were traditionally treated with medical management alone.

CONCLUSIONS

With continued high quality research and an increasing body of evidence, interventional bronchoscopy has enormous potential to provide both safe and effective options for patients with a variety of lung diseases.

Bronchoscopic Treatment of Airway Obstructions With a Novel Electrosurgical Device

OBJECTIVES

Airway obstructions (AOs) in the central airway or lobar bronchi develop due to malignant or benign disease. Because of the morbidity and mortality associated with AO, it is important to develop additional therapeutic ablative techniques. CoreCath2.7S is a novel monopolar radiofrequency electrosurgical device approved to treat obstructions of the upper airway and tracheobronchial tree by both cutting soft tissue and providing electrosurgical hemostasis. We present a large case series describing its use.

METHODS

Retrospective chart review was performed of all patients with AO undergoing airway recanalization with CoreCath2.7S at 2 interventional pulmonology practices from October 2017 to May 2019. Demographic information, AO etiology, location, and degree, and therapeutic modalities used were recorded.

RESULTS

Fifty-three patients underwent 64 procedures for AO due to malignant (n=30, 57%) or benign (n=23, 43%) disease. AOs were treated in the trachea (n=28), mainstem bronchi (n=23), and lobar bronchi (n=17). All AO occluded the airway at least 50%. Adjunctive therapeutic modalities were commonly used (n=60, 94%), including flexible cryoprobe (n=33), balloon dilation (n=23), rigid bronchoscopy (n=19), spray cryotherapy (n=19), argon plasma coagulation (n=14), and stenting (n=5). Restoration of airway patency was achieved in all cases without any periprocedural or immediate postprocedural complications.

CONCLUSION

CoreCath2.7S was successfully used to treat patients with AO due to malignant or benign disease. Airway patency was restored with no periprocedural or immediate postprocedural complications. It should be considered as another therapeutic modality in the growing field of ablative techniques for the treatment of AO.

Bronchoscopic treatment of inoperable nonsmall cell lung cancer

Patients with unresectable lung cancer range from those with early-stage or pre-invasive disease with comorbidities that preclude surgery to those with advanced stage disease in whom surgery is contraindicated. In such cases, a multidisciplinary approach to treatment is warranted, and may involve medical specialties including medical oncology, radiation oncology and interventional pulmonology. In this article we review bronchoscopic approaches to surgically unresectable lung cancer, including photodynamic therapy, brachytherapy, endoscopic ablation techniques and airway stenting. Current and past literature is reviewed to provide an overview of the topic, including a highlight of potential emerging approaches.

Robotic bronchoscopy for pulmonary lesions: a review of existing technologies and clinical data

Bronchoscopic interventions are preferred for sampling suspicious pulmonary lesions as they have lower complications and can achieve diagnosis and staging in one single procedure. Limitations in existing guided bronchoscopy platforms has led to developments in robotic assisted technologies. These devices may allow the bronchoscopist to more precisely maneuver the scope and instruments into the periphery of the lungs under direct visualization while also ensuring stability during sampling of the target lesions. These devices have the potential to improve the diagnostic yield in sampling peripheral lung lesions and may play a role in the treatment of non-operable or oligometastatic peripheral tumors using bronchoscopic ablative therapies. In this article, we review the existing robotic bronchoscopy technologies and summarize the available pre-clinical and clinical data supporting their use.