Introduction
The goal of this chapter is to provide an effective, systematic, multimodality bronchoscopic approach to the problem of malignant airway obstruction that facilitates proper integration of all of the various technologies currently available. The approach outlined is multimodality and focuses on bronchoscopic interventions, but bronchoscopic interventions are just one component of the multidisciplinary care of the cancer patient, so we will also discuss how and when bronchoscopic interventions should be integrated with chemotherapy, radiation therapy, and surgery.
To do this we will first establish a clear classification system for the different types of malignant airway obstruction. Different types of malignant airway obstruction are best treated by different techniques. The focus is on the decision process of when to use a given technique and how to integrate multiple techniques into a unified approach. The details of how to do the actual techniques are provided in other chapters. We will then use this classification scheme to delineate the indications for therapeutic bronchoscopy for malignant airway obstruction, preprocedural management, intraprocedural management, and postprocedural management.
Types of Malignant Central Airway Obstruction
Malignant central airway obstruction occurs frequently in patients with lung cancer and in patients with pulmonary metastases from other malignancies, including breast, colon, and renal cell cancer. Central airway obstruction in this case refers to an obstruction in the trachea, mainstem bronchi, bronchus intermedius, or at the entrance of a lobar orifice. There are three main types of malignant airway obstruction: endobronchial, extrinsic compression, and a mixed pattern ( Fig. 14.1 ). Endobronchial obstructing tumors are typically polypoid or fungating and are predominantly intraluminal with a relatively intact bronchial wall such that if the intraluminal component of the tumor is destroyed, the airway has sufficient structural integrity to remain open with a normal luminal diameter thereafter. Extrinsic compression by tumors can also lead to obstruction. In cases of extrinsic compression, the airway wall itself may be tumor free, but the mass effect of the tumor compresses the airway to such a degree that the airway is compromised. Of course, many lesions demonstrate a mixed pattern of disease, with some intraluminal tumor as well as some airway compression.
The type of intervention chosen depends on the type of malignant airway obstruction. Ablative techniques that destroy tissue are useful for malignant endobronchial obstruction. Ablative techniques include lasers, electrocautery, argon plasma coagulation (APC), photodynamic therapy, microdebriders, cryotherapy, and mechanical debridement. Stents are the primary modality for patients with malignant extrinsic compression leading to airway compromise. For patients with a mixed pattern of disease, multiple modalities are usually required. Typically the endobronchial component of the obstruction will first need to be ablated followed by stenting if required.
Indications for Bronchoscopy in Patients with Malignant Central Airway Obstruction
Indications for bronchoscopic intervention include relief of obstruction that is causing dyspnea, infection, or clinically significant bleeding. Although therapeutic bronchoscopy in this setting may indeed prolong life modestly for some patients (e.g., enable them to get off the ventilator), the majority of patients benefit from changes in quality of life rather than duration. When deciding whether to perform therapeutic bronchoscopy for malignant central airway obstruction it is important to consider:
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The probability of technical success, defined as the probability of being able to reestablish and maintain central airway patency at ≥50% of normal.
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How likely is it that the procedure, if technically successful, will also result in a clinically meaningful improvement in dyspnea and health-related quality of life (HRQOL)? A procedure that is technically successful (i.e., 100% reopening of a previously 70% obstructed left mainstem bronchus) may or may not result in a clinically significant improvement in dyspnea.
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The risk if the obstruction were to remain unrelieved versus the risks of the procedure. Both short-term and long-term risks need to be considered.
Technical Success
Clinically significant malignant central airway obstruction is typically defined as ≥50% obstruction of the cross-sectional area of the trachea, mainstem bronchi, bronchus intermedius, or a lobar orifice. Obstructions involving <50% of the cross-sectional area of the airways are less likely to cause symptoms and are likely to have little or no immediate physiologic impact. Bronchoscopic intervention is usually warranted for symptomatic lesions resulting in ≥50% obstruction, provided that there are patent airways with viable lung distal to the obstruction. If the airways distal to the obstruction are themselves occluded or the lung is nonviable, then relief of the central airway obstruction will not result in any meaningful improvement, so therapeutic bronchoscopy is not warranted. Of course, obstructing lesions can grow, so a 40% obstruction that is asymptomatic may progress to 80% obstruction with symptoms in the future. Therefore in select cases of asymptomatic central airway obstruction that are <50%, bronchoscopic intervention may be warranted if the probability of disease progression in the future is high.
Technical success of therapeutic bronchoscopy in this context is therefore defined anatomically. A technically successful bronchoscopy is one that relieves the targeted anatomic obstruction(s) such that central airway patency is >50% of normal upon completion of the procedure. It is a short-term outcome, since the airways may close back up in the future. Factors associated with a higher probability of technical success include endobronchial lesions (as opposed to extrinsic compression or mixed obstructions) and placement of airway stents. Factors associated with a lower probability of technical success include American Society of Anesthesia (ASA) score >3, renal failure, primary lung cancer (as opposed to other types of cancer), left mainstem disease, and tracheal-esophageal fistula.
Impact on Dyspnea and HRQOL
It is important to remember that therapeutic bronchoscopy for malignant central airway obstruction is essentially a palliative intervention, since most patients have advanced disease that is incurable. So while relief of anatomic obstruction defines technical success, this is only a short-term tactical goal of bronchoscopic intervention. The true strategic goal is to decrease dyspnea, improve HRQOL, and improve quality-adjusted survival. Not every patient with a technically successful procedure will have a meaningful improvement in dyspnea and quality-adjusted survival. Clinically significant improvement in dyspnea occurs in approximately 50% of patients undergoing therapeutic bronchoscopy, whereas clinically significant improvement in HRQOL occurs in 40%. Patients with more shortness of breath at baseline (as measured by the Borg score) are more likely to experience significant improvements in dyspnea and HRQOL. Conversely, patients with lobar obstruction (as opposed to obstruction in the mainstem bronchi, bronchus intermedius, or trachea) are less likely to have a significant improvement in dyspnea or HRQOL. The magnitude of the improvement in HRQOL is also associated with higher ASA score and lower functional status. Thus patients at the highest risk for complications also often have the greatest potential for benefit.
Hazard of Delay in Therapeutic Bronchoscopy Versus Procedural Risks
In patients with obstruction <50% who are asymptomatic, options include observation versus proceeding with therapeutic bronchoscopy. The benefit of observation is that it avoids procedural risk, and if there are other treatment alternatives (e.g., radiation therapy or chemotherapy), it provides time for these treatments to take effect, and if the patient responds to those treatments and the airway obstruction improves, the risk of the procedure may ultimately be avoided altogether. The risk of observation is that the malignant airway obstruction will worsen, symptoms will develop, the procedural difficulty will increase, the risk of complications will increase, and the probability of technical success will go down. In essence, the hazard of delay in asymptomatic patients is that the window of opportunity when it is possible to intervene with a low-risk procedure will be missed.
Balancing the hazard of delay versus the risks of immediate intervention in these patients therefore requires a global and multidisciplinary perspective. In patients who are treatment naive with tumors that are likely to respond rapidly to treatment, it is often reasonable to proceed with chemotherapy and radiation first, provided that the patient is followed closely as an outpatient. There should be a low threshold to change strategy and intervene with therapeutic bronchoscopy if dyspnea develops or there is radiographic worsening. Conversely, in patients who are not treatment naive and are unlikely to have a rapid dramatic response to chemotherapy and radiation, early intervention is often the more prudent strategy, since it will minimize the aggregate risk of procedural complications and disease progression while maintaining HRQOL.
Preprocedural Management
The decisions to intervene and the preprocedural management of the patient, although discussed separately, really are performed simultaneously and in parallel. The decision to intervene and the preparation for the procedure are closely interlinked, and each process informs the other. Preprocedural management should take into account factors that impact technical success, as noted earlier. The goal is to optimize care and position everything to maximize the chances of technical success while mitigating risk as much as possible.
Imaging is fundamental to proper preparation. Imaging facilitates planning of the procedure and allows identification of the extent of disease. Obtaining old computed tomography (CT) images is a vital part of this process. A key determinant of both technical success and the impact of bronchoscopy on HRQOL is the extent of disease in the lung distal to the obstruction. If the distal lung is nonviable, then reopening the airway to that lung is not likely to have a meaningful impact on HRQOL. Often patients will present with significant atelectasis and collapse of either a lobe or an entire lung. The extent of disease in the lung distal to the obstruction may not be visible on CT imaging after this occurs, since it will be impossible to distinguish atelectasis from diseased lung. It will also not be visible bronchoscopically prior to intervention. However, old imaging can be very helpful in identifying how much viable lung remains distal to the obstruction. If recent prior CT scans demonstrate viable lung distal to the obstruction without significant disease, intervention is probably warranted. In addition, old scans may be able to show the origin of the obstruction (e.g., whether a polypoid lesion in the left mainstem bronchus grew out of the superior segment of the left lower lobe or from the left upper lobe), which will be useful information when resecting the lesion.
Patients should be optimized from a medical perspective, with special attention to cardiac risk factors and hemostasis considerations. Standard preoperative laboratories include prothrombin time (i.e., international normalized ratio [INR]), partial thromboplastin time (PTT), complete blood count (CBC), chemistries, and a type and screen. Anesthesia preoperative clearance is usually prudent, especially in difficult cases.
Careful preparation prior to the procedure is essential, and communication between the interventional pulmonologist and bronchoscopy technicians and nurses is vital. This should be done prior to the case so that all the necessary equipment is set up ahead of time and is within easy reach in case there is an emergency. Most cases of malignant airway obstruction should be approached with the rigid bronchoscope (with flexible bronchoscopy being done through the rigid as needed). Occasionally simpler cases (e.g., an endobronchial lesion that is only 10% obstructing a segment that requires APC for intermittent hemoptysis) may be performed with the flexible bronchoscope through an endotracheal tube. However, the ability to rapidly escalate the level of care when required is essential. In the event of an airway emergency, there may not be time to get and set up the necessary equipment. So even when doing “simple” cases with the flexible bronchoscope through an endotracheal tube, the rigid bronchoscope should be set up and ready to go within arm’s reach. Careful communication with bronchoscopy technicians and nurses can facilitate this. All of the required equipment should be set up prior to the start of the procedure and tested as appropriate. At a minimum, this should typically include:
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Rigid bronchoscope and rigid bronchoscope equipment (e.g., suction, forceps)
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A large therapeutic bronchoscope and a smaller scope (for getting through narrow openings to visualize the airways distal to the lesion)
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Tools for rapid thermal ablation of endobronchial lesions (e.g., electrocautery probe, yttrium aluminum garnet [YAG] laser, yttrium aluminum perovskite [YAP] laser)
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Stents of appropriate sizes and fluoroscopy readily available if metal stents are planned
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Cryotherapy probe for removal of clots in case bleeding occurs
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Bronchial blocker readily available.
In addition, communication between the interventional pulmonology team and the anesthesia team is essential. General anesthesia is usually preferred. Although therapeutic bronchoscopy can be done using moderate sedation, it is associated with higher complication rates. Prior to the procedure, there should be a review of the management plan for the patient with anesthesia and interventional pulmonology teams. This should include a clear airway plan (e.g., intubation with an endotracheal tube vs. laryngeal mask airway for airway inspection vs. intubation with the rigid bronchoscope from the beginning), the method of ventilation planned (e.g., jet ventilation via the rigid bronchoscope vs. volume cycled), the types of ablative techniques that are likely to be used (e.g., electrocautery probe vs. APC vs. laser), whether or not stenting is likely to be required, and contingency plans for difficult airways and emergencies.
Intraprocedural Management
The initial portion of the procedure should in general follow the plan that was carefully developed and communicated with the anesthesia and bronchoscopy teams as outlined earlier. Establishment of an airway will be achieved, usually with either the rigid bronchoscope or an endotracheal tube. Next the airway examination should be completed, and the malignant airway obstruction should be evaluated and classified by the bronchoscopist as either being due to endobronchial disease, extrinsic compression, or a mixed pattern, as described earlier. After careful consideration of the full medical context (e.g., is the patient treatment naive or is this purely palliative), severity of dyspnea, probability of technical success, and probability of having a meaningful improvement in HRQOL, the bronchoscopist will have to reach a final decision as to whether or not intervention is warranted.
Assuming that intervention is indeed warranted, intraprocedural decision-making and management will follow an iterative algorithm consisting of:
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Assessment of obstruction type and severity
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Application of an appropriate interventional modality (e.g., electrocautery)
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Analysis of response/success as the modality is applied
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Determining whether ongoing intervention is still required
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If intervention is still needed, return to step 1.
Assessment of obstruction type will drive intervention selection. For endobronchial lesions, ablative therapies will be the best option. Often a variety of different ablative therapies will be used in the same case, with the bronchoscopy team switching between modalities. For example, initial tumor ablation might begin with YAG laser therapy for a polypoid lesion obstructing the bronchus intermedius ( Fig. 14.2 ). As the tumor is ablated, the bronchoscopist might switch to contact electrocautery with the rigid electrocautery suction probe for particularly difficult-to-reach areas in order to achieve tumor ablation and in order to suction blood that might be oozing from the tumor. The rigid electrocautery suction probe offers the benefit of both suctioning out blood while simultaneously coagulating the tumor. The bronchoscopist might then proceed with mechanical debridement until the cauterized tissue was removed. At that point additional oozing of blood might indicate the need for additional hemostasis (since the coagulated tumor has been removed, revealing untreated tumor below it) and another cycle of ablation might begin, this time starting with the electrocautery suction probe. Eventually, with good control of hemostasis and good coagulation and debridement, the distal side of the obstruction might be visible enough that mechanical coring out could be done with the rigid scope, reestablishing a secure patent airway ( Fig. 14.3 ). Note the iterative pattern: hemostasis and coagulation with an ablation tool followed by mechanical resection, reassessment, and repeat as needed. It is critical to achieve good coagulation with an ablation device prior to mechanical resection in order to avoid bleeding complications.
