Key points
- Solitary lung nodules are commonly found in the era of expanding lung cancer screening pilot programmes, increasing the downstream costs for investigations
- Robotic-assisted bronchoscopy (RAB) platforms have been establishing their usefulness, safety and effectiveness
- Adjunct imaging is paramount in order to achieve higher diagnostic yield
- RAB has the potential to reduce benign resection rates and maybe speed-up the lung cancer pathway if cancer is confirmed
- Future potential for diagnosis and treatment in one session (ablation)
- Setup costs remain high, but there is future potential of reduced downstream costs compared to current strategies
What does the current landscape look like in interventional bronchoscopy?
As lung cancer remains the leading cause of cancer-related death, access to peripheral small lung lesions is now more than ever a necessity. Lung cancer screening programmes get increasingly established and expand around the globe, and lung nodules are a very common finding in cross-sectional imaging of the target high-risk population (i.e. 50-80 years old, current or previous history of smoking, family history of lung cancer). A multimodality evaluation of lung nodules would further reduce the time to diagnosis, and treatment if a lung cancer is confirmed. Although the bronchoscopic equipment has improved with better manoeuvrability and smaller diameter to allow farther reach within the lung, the yield is still quite low especially in the absence of real-time imaging.
The ultimate goal is to provide excellent reliable real-time image guidance during the procedure and in turn increase the diagnostic yield, and reduce complication rates.
Can you elaborate on the current challenges in this area?
The main key principles have remained the same over the years, regarding the sampling of a suspicious lung nodule: a) navigation to the lesion, b) tool-in-lesion confirmation, c) adequate tissue biopsy. Electromagnetic navigational bronchoscopy (ENB) incorporates CT scan data from the patient in order to enhance the process of locating the lesion, however the yield of ENB alone has not been a major jump forward when compared to radial endobronchial ultrasound probes (EBUSMajor caution should be given when interpreting diagnostic yields from the published clinical trial data, as the different tools/technologies and definitions of ‘diagnostic biopsy’ are not standardised, causing challenges.
Furthermore, techniques like radial EBUS, ultrathin bronchoscopy and ENB, require from the operator to navigate to a peripheral lesion, ensure that they maintain the bronchoscope in a set position, and obtain enough tissue material for accurate diagnosis while at the same time consider the breathing motion artifact. Another major factor that affects yield in ENB is the well recognised issue of CT-to-body divergence (CTBD).
Regardless of the navigation platform used, a planning CT is created with a thin-slice end-inspiratory phase CT chest. This manoeuvre enhances the airway segmentation on the planning software, which in turn helps the path selection during navigation. The lung lesion of interest is then identified on the virtual airway tree created by the software, and the relationship to the adjacent airway is defined. During the procedure, there is a process of synchronisation of the airway, the relative location of the lung lesion of interest, the position of the robotic bronchoscope, and the patient’s true in vivo anatomy. After this step, the bronchoscopist navigates to the target lesion by using the virtually mapped pathway. However, the lung volume of the CT scan used for procedural planning is always different than the patient’s real-time lung volume during the procedure, especially when the procedure is being appropriately done under general anaesthetic and muscle paralysis. Inevitably this leads to CTBD. This is the difference between the lung lesion location at the time of CT planning and at the time of procedure. Additionally, the development of atelectasis during the procedure related to ventilation strategies, oxygen supplementation, and manipulation of the airway with tools, commonly lead to further worsening of CTBD. Therefore, a further challenge is that the navigation system could be misled and provide false reassurance of localisation.
As those issues become more commonly encountered, there is an increased effort in the development of advanced imaging to support the existing RAB platforms. The ultimate goal is to provide excellent reliable real-time image guidance during the procedure and in turn increase the diagnostic yield, and reduce complication rates.
While this is certainly an exciting field with potential to improve patient care, careful planning is paramount when comes to commencing any relevant service to areas of interest, as the usual caveats of inequalities of access and cost-benefit analyses will need strong clinical input, and every step on the way must be evidence-based.
What does the potential look like in terms of therapeutics and diagnostics?
Due to the wider use of cross-sectional images during acute admissions in elderly population with multiple comorbidities, it is expected that we will inevitably see a rise in the detection of inoperable early-stage lung cancers in patients with multiple co-morbidities and / or poor performance status. An alternative to curative surgery is stereotactic body radiation therapy (SBRT) which also has its own limitations in terms of toxicity and proximity of the lesion to vital anatomical structures (‘no-fire zones’). Multiple societies including CHEST, the NCCN (National Comprehensive Cancer Network), and the Society of Thoracic Surgeons suggest image-guided thermal ablative (IGTA) therapy for inoperable early-stage lung cancer. IGTA is a form of local ablative therapy that includes radiofrequency ablation (RFA), microwave ablation (MWA), and cryotherapy ablation (CA). Previously, this form of treatment has been performed with a percutaneous approach using cone-beam CT, ultrasound (US), and CT fluoroscopy; however, significant adverse events have been reported including pneumothorax in up to 45%, chest tube insertion required in about 20% of patients, and pulmonary haemorrhage has been reported in 6% of the cases with 2% requiring intervention.
This is where the potential of ENB to utilise ablation techniques comes in to play. There are only a handful of studies in progress at the moment worldwide, but key-opinion leaders, including those from across the UK, are navigating the way forward.
Looking at the existing literature, studies suggest that a bronchoscopy-guided approach for ablation of peripheral lung tumours is technically feasible. There is a strong signal of the potential added benefit of lower complications, however major caution is needed when interpreting complication rates in small study populations, with very wide variability in skillset and overall healthcare setups which are rarely reproducible due to the costs involved. Real-time imaging during ablation techniques is certainly of utmost importance.
And if you had to summarise your conclusions and any future considerations, what would you want us to know?
Common themes for all of the above new advanced techniques are the very high cost of initial setup, staff training, ongoing maintenance of a high-quality service and equipment, additional multi-disciplinary workload, and patient selection. While this is certainly an exciting field with potential to improve patient care, careful planning is paramount when comes to commencing any relevant service to areas of interest, as the usual caveats of inequalities of access and cost-benefit analyses will need strong clinical input, and every step on the way must be evidence-based.