Narrative review of malignant central airway obstruction: management updates

Introduction

Background

Malignant central airway obstruction (MCAO) is defined as significant and usually symptomatic narrowing of the trachea, main stem bronchi or the bronchus intermedius from a neoplastic process (1). While central airway obstruction (CAO) is traditionally defined as a greater than 50% narrowing of the airway lumen (2), significant flow-limitation leading to dyspnea is not usually perceived until the airway narrowing is more than 70% (3). Primary lung cancers are associated with MCAO in 13% of the cases at diagnosis, and an additional 5% develop MCAO later in the course (4). Common etiologies for non-lung MCAO include renal, colon, thyroid, and head and neck primaries, amongst others (5).

MCAO can be morphologically classified into three types: intrinsic, extrinsic, and mixed pattern. Intrinsic disease typically originates within the airway lumen and is characterized by a relatively intact bronchial wall (6). As a result, the airway retains enough structural integrity to remain open once the intraluminal component of the tumor is addressed using ablative therapies (Figure 1). Non-ablative, mechanical debulking techniques, such as the use of forceps or tumor-coring with the edge of a rigid bronchoscope, can also be used to re-establish airway patency. However, our document focuses on commonly used ablative modalities as highlighted in the sections below. Extrinsic compression collapses the airway due to external pressure and usually warrants stent placement to reopen the airway (Figure 2). Lastly, in the mixed type, both intrinsic and extrinsic factors contribute to the obstruction, often necessitating a combination of ablative therapy followed by stent placement to re-establish and maintain airway patency (Figures 3,4).

Figure 1 Endobronchial tumor before and after debulking. (A) An intrinsic/endobronchial lesion seen is completely obstructing the distal LMB. (B) The lesion was fully extracted using an EC snare and cryotherapy to completely recanalize the airway. The lesion was identified as a leiomyoma on pathology. EC, electrocautery; LMB, left main bronchus.

Figure 2 Extrinsic CAO with airway recanalized after airway stenting. (A) A purely extrinsic morphology CAO was managed with (B) silicone Y-stent placement to re-establish airway patency. CAO, central airway obstruction.

Figure 3 Mixed intrinsic and extrinsic CAO managed with debulking. (A) A mixed morphology lesion, predominantly intrinsic seen here to be severely obstructing the distal tracheal lumen. The lesion was resected using an EC snare and cryo-debulking, followed by APC. (B) The airway lumen was near completely recanalized, with minimal residual extrinsic compression that did not warrant stenting. The lesion was identified as an extranodal marginal zone lymphoma on pathology. APC, argon plasma coagulation; CAO, central airway obstruction; EC, electrocautery.

Figure 4 Mixed intrinsic and extrinsic CAO managed with airway stenting. (A) A mixed morphology lesion, predominantly extrinsic, in the distal trachea was treated with cryo-debulking. The stenotic index (from extrinsic compression) of the airway remained >70% after debulking the intrinsic component and therefore, (B) an airway stent was placed to re-establish luminal patency. CAO, central airway obstruction.

MCAO may cause dyspnea, cough, or hemoptysis, amongst other symptoms. Retained secretions may lead to post-obstructive pneumonia. Early recognition of MCAO is critical for effective management, as unaddressed MCAO can lead to respiratory distress and is often life-threatening, with a poor 5-year survival rate (7) and an increased hazard ratio for death (4). Successfully re-establishing airway patency can lead to symptomatic improvement in more than 90% of patients, often with reported improvement in performance status and pulmonary function testing (8). In those with CAO requiring mechanical ventilatory support, an intervention to relieve the CAO can lead to prompt liberation from the positive pressure in about 90% of cases, especially if the intervention is performed early (9,10). Moreover, once intervened upon, the survival curves for patients with MCAO match those for those without MCAO (11).

Objectives

This article aims to provide a comprehensive overview of MCAO management. While most therapeutic interventions have been used for a few decades, recent data, guidelines, and updates in modalities are allowing a more nuanced and evidence-based approach to MCAO management (1). We present this article in accordance with the Narrative Review reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1677/rc).

Methods

Information used to write this paper was collected from the sources are listed in Table 1. The search strategy summary can be found in Table 2.

Discussion

Bronchoscopic ablative therapies

Since Gustav Killian first used a bronchoscope to remove a foreign body from a farmer’s trachea in 1898, and with the introduction of the fiberoptic bronchoscope by Japanese surgeon Shigeto Ikeda in the late 20^th century, numerous bronchoscopic techniques have been developed to treat CAO (12). Bronchoscopic interventions have proven to be safe, improve quality of life, and potentially extend survival in patients with MCAO, particularly when performed on critically ill patients or when followed by systemic therapy (10). Debulking tumor may make parenchymal sparing surgeries feasible (13), and the use of multimodal treatment may be superior for local control and symptom improvement (14-16). In general, patients with greater baseline dyspnea and functional limitations may benefit more from these interventions, possibly due to the ability to achieve a larger demonstrable change (17). It is, however, crucial to select patients well—those with attributable symptoms to the CAO to achieve demonstrable “clinical”, and not just “technical” success. It is crucial for bronchoscopists to understand the principles of use, indications, and potential complications of various ablative modalities to effectively restore airway patency in the treatment of MCAO. As mentioned above, the use of ablative tools is to address intrinsic/endobronchial tumor and the intrinsic component of mixed morphology disease.

Laser

Laser light is characterized by three key properties: monochromaticity (single wavelength of light), coherency (light waves in phase), and collimation (light waves traveling in parallel rays). When laser light contacts tissue, its energy is absorbed, creating a thermal effect that allows for both cutting and coagulation. The thermal effect depends on several laser properties (18). The modifiable properties include the power setting and the distance of the laser fiber from the lesion (power density). High power density can be achieved by either increasing the power output (shorter wavelength) or decreasing the fiber-to-tissue distance, which results in tissue carbonization and vaporization (19). Lower power density can be achieved by lowering the power output or increasing the fiber-to-tissue distance, resulting in broader coagulation. Non-modifiable properties include the laser medium and target tissue chromophore. Various types of lasers exist, each using different media to generate light (20).

The most frequently used laser in managing both malignant and benign endobronchial disorders has historically been the neodymium:yttrium aluminum garnet (Nd:YAG) (21). Its balanced ability to both vaporizes and coagulate tissue makes it preferable for mechanical debulking, often after ‘cooking’ the tumor to devascularize it first (18,20). The Nd:YAG laser has a wavelength of 1,064 nm, which lies in the infrared region and is invisible to the human eye. It can penetrate up to 10 mm of tissue, as it is less absorbed by hemoglobin compared to the argon laser (488 or 514 nm), which uses blue-green light and is absorbed by hemoglobin, limiting tissue penetration to 1–2 mm (22,23). Given the deeper tissue penetration of the Nd:YAG laser, a conservative approach and frequent re-evaluation of the lesion are recommended, as the depth of tissue penetration may not be immediately apparent (24).

Laser-assisted bronchoscopic debulking, in experienced hands, has been shown to restore airway patency in more than 90% of cases (24,25), which consequently improves patient performance status, enhances their ability to tolerate chemotherapy or surgery (26) and may enable parenchyma-sparing surgery (27,28).

A few complications have been reported with laser therapy. Due to the high depth of penetration, incorrect use may lead to airway perforation (29). The risk of perforation can be minimized by avoiding direct contact with the airway wall or tumor, limiting penetration depth (using power <40 W and pulse duration <1 second), and keeping the laser fiber aligned with the airway axis (18). Airway fire is extremely rare and can be prevented by reducing inspired oxygen concentration to less than 40% and keeping anything combustible, such as the endotracheal tube, a fair distance away from the laser fiber (30). Provider eye-protection with laser specific eyewear (goggles) may be necessary to prevent complications from back scatter of the radiation.

Contact and non-contact electrocautery (EC)

EC uses electrical current to heat, coagulate, carbonize, and vaporize tissues. Coagulation occurs at 60–70 ℃, desiccation at temperature above 100 ℃, carbonization above 200 ℃, and vaporization at 300 ℃ (19,31). Generally, higher power settings result in shallower but more rapid effects. Other factors, such as tissue composition, application time, and the pressure exerted by the tool (in contact mode), also influence the outcome (32).

Compared to laser therapy, where the depth of penetration cannot be accurately assessed, EC offers the advantage of visually confirming the extent of effect, with an expected penetration depth of 1 to 2 mm (33). The charred tissue is resistant to deeper effects and must be periodically debulked with forceps. This is not necessary with the cautery is being used for hemostasis alone. Various tools can be used as an EC, including snares, knives, probes, and forceps, depending on the desired effect. For example, a snare device can be applied to a pedunculated lesion, cauterizing the stalk for complete resection while preserving the tissue for pathological analysis (34) (Figure 5).

Figure 5 Endoluminal carcinoid before and after debulking. (A) A lesion (identified as a typical carcinoid on path) completely occluding the left main bronchus. (B) It was resected using an EC snare. EC, electrocautery.

Argon plasma coagulation (APC) is a form of EC that operates in a non-contact mode. In APC, argon gas flows through a probe containing a tungsten electrode at its tip. A high-frequency electric current passing through the electrode ionizes the argon gas, which is then released at the probe’s tip as plasma. This allows the treatment of lesions lateral to the probe, as well as other areas that might be difficult to access for traditional tools. The increased resistance of coagulated tissues suppresses further conduction and limits tissue penetration, enabling the transfer of electrons to adjacent untreated areas (35,36). If the probe is close to normal mucosa, as may happen with coughing, poor maneuvering, and sometimes, even regular respiratory movement or cardiac pulsations, collateral thermal injury may occur.

APC, as per the AQuIRE registry, is the most used ablative modality for MCAO (35% of cases), followed by laser therapy (23%) and contact EC (21%) (37). The success rate in achieving airway recanalization ranges from 67% to 95% (38-40). APC has also been used with curative intent for early-stage intraluminal squamous cell lung cancer and to treat the base of intraluminal typical carcinoid tumors that are managed bronchoscopically alone (as a tissue-sparing alternative) (41,42).

Known complications of EC, similar to those of laser therapy, include bleeding, endobronchial fire, and airway perforation. Due to a shallow depth of penetration of EC, perforation is rare. As mentioned previously, airway fire can be prevented by maintaining a fraction of inspired oxygen (FiO₂) of less than 0.4 during the procedure. Uniquely, incorrect APC use can result in gas emboli (43); the risk of which can be minimized by keeping gas flow below 0.8 L/min, suctioning during activation, and avoiding its use in confined spaces (such as in lobar airways). Another important consideration with EC is its potential interference with implanted cardiac devices, as EC signals during continuous activation for a few seconds may be misinterpreted as abnormal intracardiac events (44). It is important to perform pre-procedural reprogramming or use an intraprocedural magnet placement to ensure patient safety.

Laser versus EC

The deeper and potentially broader scope of effect with lasers may allow for a faster procedure than EC. Though care must be taken to appropriately align the probe to minimize undesired deeper tissue effects that may result in airway injury or perforation. EC use requires patience due to a relatively superficial effect, and the charred tissue must periodically debulked. However, its use may be cheaper and safer (45). One of the challenges with thermal modalities is that the FiO₂ must be maintained less than 0.4 to avoid airway fires. This often makes it challenging to use these therapies in patients who are very hypoxic to begin with or with low respiratory reserve. In such situations, the use of non-thermal modalities may be considered (elaborated upon below).

Photodynamic therapy (PDT)

PDT involves the use for a photosensitizing agent, such as porfimer sodium (Photofrin), which is activated by a non-thermal laser to induce a phototoxic reaction leading to cell death (46). The agent is injected systemically and preferentially absorbed by malignant cells. It is then washed out of non-tumoral, normal cells within 2–3 days after injection. Approximately 72 hours post-injection, targeted laser therapy (630–680 nm wavelength for Photofrin) is applied to the target tissue during bronchoscopy. As the laser is absorbed, this process generates reactive oxygen species and free radicals leading to both direct physical (type II photooxidation reaction) and local immunological effects (32). The duration of light treatment dictates the energy delivered, typically 200 J/cm² (400 mW/cm for 500 seconds), although the energy level should be adjusted based on tumor size and desired effect (47,48). The usual depth of tissue destruction ranges from 5 to 10 mm, depending on local tissue oxygenation and pigmentation (49). Tumor necrosis begins within hours of illumination, and the sloughing of tissues can temporarily worsen airway obstruction (18). Debridement is then performed via subsequent bronchoscopy within 2 days after the maximal effect is achieved.

PDT has shown to improve dyspnea and achieve airway patency in about 80% of patients with MCAO (50,51). PDT is also used in multimodal treatment approaches for management MCAO, in combination with other therapies like radiation, laser debulking, and systemic chemotherapy (52-54). The bulk of evidence for the use of PDT in the airways comes from curative treatment for early-stage lung cancer of the airway (and not MCAO) with remission rates as high as 83% (55). This capitalizes only an advantage of PDT wherein it likely treats disease not visible to the naked eye. The primary disadvantage of PDT however, is its delayed cytotoxic effects, which make it unsuitable for symptomatic and/or severe cases of MCAO that warrant prompt airway recanalization. The most common side effect is photosensitivity, due to the accumulation of the photosensitizing agent in the skin, requiring patients to avoid sun and bright light exposure for several weeks post-procedure (32). Other side effects include respiratory distress from airway edema or tissue sloughing, which can worsen obstruction, and hemoptysis, or rarely lead to strictures. PDT is generally contraindicated for lesions with tracheoesophageal fistula or those adjacent to major blood vessels (18). As a general rule, we avoid PDT when the distance from the luminal aspect of the lesion to the nearest vessel is less than 1 cm.

Cryotherapy

In cryotherapy, a cryoprobe’s small orifice allows liquefied gas under pressure (N₂O at −89 ℃; CO₂ at −78.5 ℃) to expand into its gaseous form, resulting in drastic pressure and consequently, temperature drops (Joule-Thomson effect). This extreme cold, reaching less than −40 ℃ at the tissue level, causes tissue destruction and cell death (56,57) as a tissue-sparing alternative due to vascular, physical, and immune-mediated effects at the cellular level (58). Vascular effects like vasoconstriction, increased viscosity, and thrombosis lead to tissue ischemia, while physical effects result in intra- and extracellular ice crystal formation, depending on the water content in cells. Cartilage and fibrous tissues are relatively cryo-resistant, which reduced the incidence of airway perforation with cryotherapy compared to other ablative therapies (56,59). Potential immune-mediated effect is believed to involve the induction of natural killer cell proliferation (57).

There are three cryotherapy techniques. Contact probe cryotherapy involves applying the cryoprobe interstitially or adjacent to the target, undergoing several 10–30 seconds freeze-thaw cycles. This technique relies mainly on delayed cytotoxic effect, making it unsuitable for symptomatic or severe MCAO cases. A follow-up bronchoscopy is required typically within a few days to remove dead tissue (60). In contrast, cryo-debulking or cryo-recanalization involves applying the cryoprobe to the target for 3–5 seconds to adhere, then pulling it away firmly from the lesion for debulking (Figure 6). This provides immediate relief (61,62). Lastly, spray cryotherapy is a relatively newer technique where cryogen remains in liquid form long enough to be sprayed directly onto tissues, freezing them at −196 ℃. It allows for rapid and uniform treatment of a large area (63,64). However, as a stand-alone modality, this too is unsuitable for immediate airway recanalization in CAO.

Figure 6 Cryo-debulking being performed to debulk an endoluminal tumor.

Cryotherapy has a success rate of 70% to 90% in treating MCAO (65,66). It may also have a synergistic, immune-mediated effect with chemotherapy or radiation (57,58). At the time of the AQuIRE registry (data collected between 2009 and 2013), cryotherapy was utilized in only 8% of cases (37).

Contact probe cryotherapy is a safe ablative technique, carrying no risk of airway fires, and a minimal risk of perforation or collateral injury (56). However, with cryo-debulking there is a significant risk (4–25%) of moderate bleeding, as the freezing effect occurs around the probe and the tumor is then sheered away (62,67). With suitable expertise in rigid bronchoscopy and/or hemoptysis management, such as use of occlusion/tamponade balloons, cryo-debulking does provide for a quick and effective way to recanalize the airway. Cryotherapy preserve tissue architecture and is very useful to use in conjunction with other ablative modalities too (e.g., to retrieve tissue after the use of an EC snare, or debulking devascularized tumor after coagulating it with a laser).

Endobronchial brachytherapy (EBBT)

EBBT involves the use of radioactive seeds, such as iridium-192, which are loaded into a catheter to deliver radiation at various dose rates for treating MCAO. These dose rates include low-dose rate (LDR), intermediate-dose rate (IDR), and high-dose rate (HDR) (68-70). LDR delivers 75–200 cGy/hour and requires prolonged exposure of 20–60 hours, necessitating hospitalization (24). IDR delivers 200–1,200 cGy/hour over sessions lasting 1–4 hours, with total doses similar to LDR (70-72). Lastly, HDR delivers over 1,000–1,200 cGy/hour with each session lasting 3–30 minutes, typically requiring three weekly sessions to achieve a total dose of 1,500 cGy (70,72). HDR is most used due to its efficiency.

A study involving 95 patients with MCAO indicated that 79% experienced improved airway obstruction post-treatment, with significant 1-year survival improvements noted among responders (73). Known complications related to EBBT include radiation bronchitis, bronchial stenosis, fistula formation, and hemorrhage (74,75).

EBBT has fallen out of favor with most bronchoscopists due to its delayed effect, potential complications, and the wide spread availability of alternate immediate-effect thermal and non-thermal ablative tools.

Microwave ablation (MWA)

MWA uses an electrode that is directly placed into a lesion, emitting electromagnetic waves that cause water molecules to oscillate, thereby increasing their kinetic energy through dielectric hysteresis. MWA systems operate at frequencies of 915 or 2,450 MHz, with respective power outputs of 45 and 140 W (76). Unlike radiofrequency ablation (RFA), MWA is not affected by insulating properties or the heat sink effect, allowing it to produce higher intratumoral temperatures over shorter application period (77). This capability results in larger ablation zones, making MWA potentially more effective than RFA.

MWA has recently been used to achieve airway recanalization and symptom relief in MCAO cases. A pilot study involving eight cases of CAO treated with MWA showed 100% successful airway recanalization with no complication (78). MWA has also been safely used in patients respiratory failure requiring high FiO₂ and those with endobronchial stents (78,79). Known complications associated with MWA include pneumothorax, with reported rates ranging from 8.5% to 63% (80), followed by bronchopleural fistula and pulmonary infection.

Due to the widespread availability of and experience with other heat and cold-based ablative tools, MWA for MCAO remains a modality in search of more data or at the very least, additive-value evidence.

Summary

The selection of a modality for ablating an endobronchial tumor is primarily influenced by the provider’s expertise, preference, and available resources. Additional considerations include tumor characteristics (such as vascularity, size, and morphology), patient-related factors (like respiratory reserve, oxygen needs, and urgency of airway recanalization), and the interplay between technology and tissue. Although no studies directly compare the efficacy of these modalities, a thorough understanding of their principles and effects enables the proceduralist to make informed decisions tailored to each clinical situation. Often, a multimodal approach is preferred to ensure a safe, effective, and successful outcome. Given the unique nature of clinical scenarios, the critical condition of patients, and the subjective assessment of procedural success, prospective head-to-head comparisons of these modalities will likely remain difficult to conduct.

Stents

The use of airway stents dates back to 1965 when Montgomery introduced a silicone T-tube to manage tracheal stenosis (81). Since then, the development of stents has evolved significantly to address extrinsic and mixed types of MCAO. When mixed morphology disease is present, tumor debulking must first be tried, and if a significant residual stenosis remains, airway stenting must be considered. For purely intrinsic disease, if the CAO is rapidly recurrent after successful debulking, warranting frequent bronchoscopies, airway stenting may be considered. However, what is ‘frequent’ is best defined by a shared decision between the provider and patient factoring in patient values and the risk of subsequent debulking bronchoscopic procedures.

Types

Currently, metal and silicone stents are predominantly used, with innovative options like three-dimensional (3D) printed stents and biodegradable stents (BDS) emerging. Stents, by re-establishing airway patency, when successful, generally provide immediate symptom relief and usually enhance quality of life (82,83). The choice of specific stent typically depends on the location and extent of airway involvement, the anatomy, and the diameter of the airway lumen (32).

Metal stents are commonly made from nitinol, a highly elastic biomaterial, and are capable of size and shape deformation, allowing them to adapt to various airways (84,85). In comparison to silicone stents, metal stents are more expensive but do not typically require rigid bronchoscopy for placement, although many practitioners still prefer using rigid bronchoscopy for better airway management and stent manipulation during procedure (86-89). Metal stents offer a higher internal-to-external diameter ratio and possibly have a lower rate of migration compared to silicone stents (86). However, they present challenges in removal once epithelialized and are prone to fragmentation—an issue not commonly seen with silicone stents. It is important to note that uncovered metal stents are rarely used in MCAO because surrounding malignant tumors can grow into the stent. Furthermore, the Food and Drug Administration (FDA) has issued a black box warning concerning the difficulties of removing these stents once they have become epithelialized in cases of benign airway disease (90). Metal stents used for MCAO today are hybrid stents, consisting of an expandable metal frame that resists compression, covered by a silicone membrane to prevent tumor ingrowth. Some designs of covered metal stents also feature uncovered portions at the proximal and distal ends to facilitate aeration and drainage of secretions (in case of a jailed airway) and mitigate migration.

Tracheobronchial Y-shaped metal stents are newly available and can be deployed using either flexible or rigid bronchoscopy. A study involving 10 patients successfully delivered Y-shaped metal stents using laryngeal mask airway (LMA)-assisted technique (91). This method was less cumbersome, shorter in duration, and did not require rigid bronchoscopy. However, these stents are not customizable and their long lengths in the central airway may lead to more subsequent complications such as mucus plugging or difficulty removing.

Silicone stents leverage the beneficial properties of silicone elastomers, or polydimethylsiloxane, known for their firmness, heat stability, and inertness to tissues (86). The most common types of silicone stents include the Y-stent, tubular stent, and Montgomery T-tube. However, many other different types of silicone stents are available in various shapes, lengths, diameters, and durometers to suit different clinical needs. Silicone stents offer the advantage of customization prior to placement, as they can be easily cut to size or to aerate a jailed airway (e.g., the right upper lobe for a right mainstem to bronchus intermedius stent) (86). Once deployed, they can also be easily repositioned using forceps. Y-shape stents are particularly advantageous for maintaining patency at the main carina, preventing distal migration, and managing bilateral bronchial involvement (86). However, as with all stents, particularly those of Y shape, the amount of plastic in the airway covering native airway mucosa should be kept to a minimum.

Outcomes and complications

Stent placement has proven effective for MCAO, offering almost immediate symptom relief. Studies on stents have reported a 90–100% technical success rate in placement and 92–94% effectiveness in relieving airway obstruction symptoms (92-94). Another study on the combined use of temporary stents with radiation therapy and/or chemotherapy in MCAO patients highlighted the clinical effectiveness of stents in palliative care, with no recurrence of obstruction symptoms post-therapy (95). Technical success however, must not be equated to clinical success. Opening airways with poorly viable or perfused downstream parenchyma and opening lobar airways may not lead to symptom relief (96). Studies on use of airway stents are challenging to accomplish, and even the only published, randomized trial for airway stenting was terminated before their target enrollment (97). This study did not demonstrate a survival advantage; it did however, demonstrate a longer duration of dyspnea improvement in the stent group.

Common complications of stent placement include migration, mucus plugging, infection, and granulation tissue formation. Silicone stents have a migration rate of 9.5% and mucus plugging of 3.6% (98), while hybrid stents show migration rate of 4–22% (99). Bacterial colonization was seen in 13–26% of patients with stent placement (100). Due to these issues, regular surveillance bronchoscopy is generally recommended for patients with stents to monitor for migration, obstruction from secretion and granulation formations. Additionally, implementing airway clearance methods, such as hypertonic saline nebulization, is advised to prevent mucus plugging (101). Proper maintenance of a stent and its timely removal when the underlying CAO is suspected to be resolved (such as after disease-directed treatment) are just as crucial as the initial stent placement. Consistent clinical follow-up is essential to ensure optimal outcomes.

3D printing

3D printing technologies, already transformative in various biologic industries, are now being utilized to create customized airway stents. Utilizing high-resolution software platforms, these technologies enable providers to generate patient-specific stents based on computed tomography (CT) scans (Figure 7). These scans offer a virtual 3D model of patient’s airway segments (102). Interventional pulmonologists play a crucial role by providing input on identifying the correct stenotic sections of the airways and matching the patient’s anatomy, especially after any ablative therapies that may have been performed prior to stent placement (103).

Figure 7 Complex morphology bronchial stenosis relieved with 3D printed airway stenting. (A) A 3D printed, customized silicone stent tailored to the patient’s airway anatomy being planned. The stent was used to re-establish luminal patency for a complex, multisegmented bronchial stenosis, (B) before stent placement, (C,D) after stent placement. 3D, three-dimensional.

The 3D virtual model is converted into a medical-grade silicone stent, which is then deployed using rigid bronchoscopy. This method of stent fabrication has been approved by the FDA, and several reports on clinical outcomes are being published. One such study involving ten patients who received a 3D printed stent reported a 3-month complication rate of 40%, including two cases of stent migration, one mucus plug, and one stent removal due to excess coughing (104). Despite these complications, the study also noted significant improvement dyspnea in 80% of the patients and a 90% rate of satisfactory congruence within the airway.

3D printed stents have the disadvantage of not being immediately available on-site and therefore, cannot be used for critical airway stenoses. Their use may be considered when conventional airway stenting is associated with excessive complications due to a poor alignment or fit. However, routine use or specific indications of use remain speculative in the absence of better data, including even larger, multicenter prospective studies.

BDS

BDS have been developed to address complications associated with traditional silicone and metal stents, such as biofilm formation and granulation responses, which often necessitate further bronchoscopic interventions, and often stent replacement. BDS is fabricated from polydioxanone, a material that maintains its integrity for 6–8 weeks and fully dissolves within 3–4 months, depending on surrounding pH (higher pH results in slower dissolving time) (105).

In a study involving 12 patients—6 with malacia and 6 with stenosis—who received a total of 57 BDS, the median stent lifespan was 112 days. The study reported improvements in symptoms and forced expiratory volume in 1 second (FEV1), with minimal complications (106). Notably, only one case of excessive granulation tissue was reported, and there were no instances of stent migration from the study. Ongoing research is evaluating the validity, safety, and effectiveness of BDS, indicating a promising future for his technology in clinical practice. Currently, there is no indication for using BDS for MCAO.

Conclusions

Future directions and conclusions

Bronchoscopic interventions for MCAO have been employed for several decades, with ongoing developments in their availability, associated training, and our understanding of their tissue effects. As anti-neoplastic treatments improve, leading to enhanced long-term survival, palliative management of MCAO will become even more critical. Effective systemic therapies will necessitate more frequent stent removal, underscoring the importance of stent selection and the need for future studies to consider this as a significant outcome. The potential role of on-site 3D printing, as well as the use of 3D-printed stents for addressing MCAO in complex morphologies, is an area yet to be explored. Additionally, the applicability of BDS for rapidly treatable tumors causing MCAO remains to be studied.

Ethical considerations, the acute nature of patient presentations, and the unique anatomical variations in each MCAO case will continue to challenge comparative prospective research. However, multicenter collaborations may help address these challenges and provide better evidence-based guidance. Integrating multimodal therapies for MCAO currently relies more on clinical expertise than on robust evidence. Key questions remain unanswered, including the optimal stent type and material, the most effective surveillance strategy (or lack thereof), and the best pulmonary hygiene practices post-stenting. It is also important that we develop quality indicators and standardized definitions for measuring thresholds to intervene and subsequent technical and clinical success. Future research should prioritize patient-centered outcomes rather than focusing solely on “technical success”.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editor (Fayez Kheir) for the series “Advances in Interventional Pulmonary” published in Journal of Thoracic Disease. The article has undergone external peer review.

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1677/rc

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1677/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1677/coif). The special series “Advances in Interventional Pulmonary” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Chaddha U, Agrawal A, Kurman J, et al. World Association for Bronchology and Interventional Pulmonology (WABIP) guidelines on airway stenting for malignant central airway obstruction. Respirology 2024;29:563-73. [Crossref] [PubMed]
2. Mahmood K, Frazer-Green L, Gonzalez AV, et al. Management of Central Airway Obstruction: An American College of Chest Physicians Clinical Practice Guideline. Chest 2025;167:283-95. [Crossref] [PubMed]
3. Brouns M, Jayaraju ST, Lacor C, et al. Tracheal stenosis: a flow dynamics study. J Appl Physiol 1985;2007:1178-84. [Crossref] [PubMed]
4. Daneshvar C, Falconer WE, Ahmed M, et al. Prevalence and outcome of central airway obstruction in patients with lung cancer. BMJ Open Respir Res 2019;6:e000429. [Crossref] [PubMed]
5. Daigmorte C, Usturoi D, Fournier C, et al. Therapeutic bronchoscopy for malignant central airway obstructions caused by non-bronchogenic cancers: Results from the EpiGETIF registry. Respirology 2024;29:704-12. [Crossref] [PubMed]
6. Sherwin RP, Laforet EG, Strieder JW. Exophytic endobronchial carcinoma. J Thorac Cardiovasc Surg 1962;43:716-30.
7. Jiang M, Xu H, Yu D, et al. Risk-score model to predict prognosis of malignant airway obstruction after interventional bronchoscopy. Transl Lung Cancer Res 2021;10:3173-90. [Crossref] [PubMed]
8. Oberg C, Folch E, Santacruz JF. Management of malignant airway obstruction. AME Med J 2018;3:115.
9. Salguero BD, Agrawal A, Kaul V, et al. Airway stenting for liberation from positive pressure ventilation in patients with central airway obstruction presenting with acute respiratory failure. Respir Med 2024;225:107599. [Crossref] [PubMed]
10. Roy P, Fournier C, Barnestein R, et al. Outcomes of Therapeutic Bronchoscopy in Malignant Airway Obstruction Causing Acute Respiratory Failure. Ann Am Thorac Soc 2024;21:833-7. [Crossref] [PubMed]
11. Chen CH, Wu BR, Cheng WC, et al. Interventional pulmonology for patients with central airway obstruction: An 8-year institutional experience. Medicine (Baltimore) 2017;96:e5612. [Crossref] [PubMed]
12. Panchabhai TS, Mehta AC. Historical perspectives of bronchoscopy. Connecting the dots. Ann Am Thorac Soc 2015;12:631-41. [Crossref] [PubMed]
13. Chhajed PN, Eberhardt R, Dienemann H, et al. Therapeutic bronchoscopy interventions before surgical resection of lung cancer. Ann Thorac Surg 2006;81:1839-43. [Crossref] [PubMed]
14. Mester E, Mester AF, Mester A. The biomedical effects of laser application. Lasers Surg Med 1985;5:31-9. [Crossref] [PubMed]
15. Canak V, Zarić B, Milovancev A, et al. Combination of interventional pulmonology techniques (Nd:YAG laser resection and brachytherapy) with external beam radiotherapy in the treatment of lung cancer patients with Karnofsky Index < or =50. J BUON 2006;11:447-56.
16. Mallow C, Thiboutot J, Semaan R, et al. External beam radiation therapy combined with airway stenting leads to better survival in patients with malignant airway obstruction. Respirology 2018; Epub ahead of print. [Crossref]
17. Ost DE, Ernst A, Grosu HB, et al. Therapeutic bronchoscopy for malignant central airway obstruction: success rates and impact on dyspnea and quality of life. Chest 2015;147:1282-98. [Crossref] [PubMed]
18. Chaddha U, Hogarth DK, Murgu S. Bronchoscopic Ablative Therapies for Malignant Central Airway Obstruction and Peripheral Lung Tumors. Ann Am Thorac Soc 2019;16:1220-9. [Crossref] [PubMed]
19. Mahmood K, Wahidi MM. Ablative therapies for central airway obstruction. Semin Respir Crit Care Med 2014;35:681-92. [Crossref] [PubMed]
20. Sutedja TG, van Boxem AJ, Postmus PE. The curative potential of intraluminal bronchoscopic treatment for early-stage non-small-cell lung cancer. Clin Lung Cancer 2001;2:264-70; discussion 271-2. [Crossref] [PubMed]
21. Zaric B, Kovacevic T, Stojsic V, et al. Neodymium yttrium-aluminium-garnet laser resection significantly improves quality of life in patients with malignant central airway obstruction due to lung cancer. Eur J Cancer Care (Engl) 2015;24:560-6. [Crossref] [PubMed]
22. Van Der Spek AF, Spargo PM, Norton ML. The physics of lasers and implications for their use during airway surgery. Br J Anaesth 1988;60:709-29. [Crossref] [PubMed]
23. McDougall JC, Cortese DA. Neodymium-YAG laser therapy of malignant airway obstruction. A preliminary report. Mayo Clin Proc 1983;58:35-9.
24. Ross DJ, Mohsenifar Z, Koerner SK. Survival characteristics after neodymium: YAG laser photoresection in advanced stage lung cancer. Chest 1990;98:581-5. [Crossref] [PubMed]
25. Ernst A, Feller-Kopman D, Becker HD, et al. Central airway obstruction. Am J Respir Crit Care Med 2004;169:1278-97. [Crossref] [PubMed]
26. Chella A, Ambrogi MC, Ribechini A, et al. Combined Nd-YAG laser/HDR brachytherapy versus Nd-YAG laser only in malignant central airway involvement: a prospective randomized study. Lung Cancer 2000;27:169-75. [Crossref] [PubMed]
27. Neuberger M, Hapfelmeier A, Schmidt M, et al. Carcinoid tumours of the lung and the 'PEPPS' approach: evaluation of preoperative bronchoscopic tumour debulking as preparation for subsequent parenchyma-sparing surgery. BMJ Open Respir Res 2015;2:e000090. [Crossref] [PubMed]
28. Schreurs AJ, Westermann CJ, van den Bosch JM, et al. A twenty-five-year follow-up of ninety-three resected typical carcinoid tumors of the lung. J Thorac Cardiovasc Surg 1992;104:1470-5.
29. Tellides G, Ugurlu BS, Kim RW, et al. Pathogenesis of systemic air embolism during bronchoscopic Nd:YAG laser operations. Ann Thorac Surg 1998;65:930-4. [Crossref] [PubMed]
30. Khemasuwan D, Mehta AC, Wang KP. Past, present, and future of endobronchial laser photoresection. J Thorac Dis 2015;7:S380-8. [Crossref] [PubMed]
31. Barlow DE. Endoscopic applications of electrosurgery: a review of basic principles. Gastrointest Endosc 1982;28:73-6. [Crossref] [PubMed]
32. Powers RE, Schwalk AJ. Overview of malignant central airway obstruction. Mediastinum 2023;7:32. [Crossref] [PubMed]
33. van Boxem TJ, Westerga J, Venmans BJ, et al. Tissue effects of bronchoscopic electrocautery: bronchoscopic appearance and histologic changes of bronchial wall after electrocautery. Chest 2000;117:887-91. [Crossref] [PubMed]
34. Hooper RG, Jackson FN. Endobronchial electrocautery. Chest 1985;87:712-4. [Crossref] [PubMed]
35. Grund KE, Storek D, Farin G. Endoscopic argon plasma coagulation (APC) first clinical experiences in flexible endoscopy. Endosc Surg Allied Technol 1994;2:42-6.
36. Farin G, Grund KE. Technology of argon plasma coagulation with particular regard to endoscopic applications. Endosc Surg Allied Technol 1994;2:71-7.
37. Ost DE, Ernst A, Grosu HB, et al. Complications Following Therapeutic Bronchoscopy for Malignant Central Airway Obstruction: Results of the AQuIRE Registry. Chest 2015;148:450-71. [Crossref] [PubMed]
38. Wahidi MM, Unroe MA, Adlakha N, et al. The use of electrocautery as the primary ablation modality for malignant and benign airway obstruction. J Thorac Oncol 2011;6:1516-20. [Crossref] [PubMed]
39. Kızılgöz D, Aktaş Z, Yılmaz A, et al. Comparison of two new techniques for the management of malignant central airway obstruction: argon plasma coagulation with mechanical tumor resection versus cryorecanalization. Surg Endosc 2018;32:1879-84. [Crossref] [PubMed]
40. Zaric B, Stojanovic G, Kovacevic T, et al. Argon plasma coagulation (APC) in relief of bulky malignant central airway obstruction due to lung cancer. Eur Respir J 2014;44:696.
41. van Boxem TJ, Venmans BJ, Schramel FM, et al. Radiographically occult lung cancer treated with fibreoptic bronchoscopic electrocautery: a pilot study of a simple and inexpensive technique. Eur Respir J 1998;11:169-72. [Crossref] [PubMed]
42. Brokx HA, Risse EK, Paul MA, et al. Initial bronchoscopic treatment for patients with intraluminal bronchial carcinoids. J Thorac Cardiovasc Surg 2007;133:973-8. [Crossref] [PubMed]
43. Reddy C, Majid A, Michaud G, et al. Gas embolism following bronchoscopic argon plasma coagulation: a case series. Chest 2008;134:1066-9. [Crossref] [PubMed]
44. Paniccia A, Rozner M, Jones EL, et al. Electromagnetic interference caused by common surgical energy-based devices on an implanted cardiac defibrillator. Am J Surg 2014;208:932-6; discussion 935-6. [Crossref] [PubMed]
45. Boxem Tv, Muller M, Venmans B, et al. Nd-YAG laser vs bronchoscopic electrocautery for palliation of symptomatic airway obstruction: a cost-effectiveness study. Chest 1999;116:1108-12. [Crossref] [PubMed]
46. Hasan T, Ortel B, Solban N, et al. Photodynamic therapy of cancer. Cancer Med 2003;7:537-48.
47. McCaughan JS Jr, Hawley PC, Brown DG, et al. Effect of light dose on the photodynamic destruction of endobronchial tumors. Ann Thorac Surg 1992;54:705-11. [Crossref] [PubMed]
48. Moghissi K, Dixon K, Stringer M, et al. The place of bronchoscopic photodynamic therapy in advanced unresectable lung cancer: experience of 100 cases. Eur J Cardiothorac Surg 1999;15:1-6. [Crossref] [PubMed]
49. Dougherty TJ, Marcus SL. Photodynamic therapy. Eur J Cancer 1992;28A:1734-42. [Crossref] [PubMed]
50. McCaughan JS Jr, Williams TE. Photodynamic therapy for endobronchial malignant disease: a prospective fourteen-year study. J Thorac Cardiovasc Surg 1997;114:940-6; discussion 946-7. [Crossref] [PubMed]
51. Minnich DJ, Bryant AS, Dooley A, et al. Photodynamic laser therapy for lesions in the airway. Ann Thorac Surg 2010;89:1744-8; discussion 1748-9. [Crossref] [PubMed]
52. Chhatre S, Murgu S, Vachani A, et al. Photodynamic therapy for stage I and II non-small cell lung cancer: A SEER-Medicare analysis 2000-2016. Medicine (Baltimore) 2022;101:e29053. [Crossref] [PubMed]
53. Moghissi K, Dixon K, Hudson E, et al. Endoscopic laser therapy in malignant tracheobronchial obstruction using sequential Nd YAG laser and photodynamic therapy. Thorax 1997;52:281-3. [Crossref] [PubMed]
54. Kimura M, Miyajima K, Kojika M, et al. Photodynamic Therapy (PDT) with Chemotherapy for Advanced Lung Cancer with Airway Stenosis. Int J Mol Sci 2015;16:25466-75. [Crossref] [PubMed]
55. Kato H, Okunaka T, Shimatani H. Photodynamic therapy for early stage bronchogenic carcinoma. J Clin Laser Med Surg 1996;14:235-8. [Crossref] [PubMed]
56. Maiwand MO, Homasson JP. Cryotherapy for tracheobronchial disorders. Clin Chest Med 1995;16:427-43.
57. Maiwand MO, Mathur PN. Endobronchial cryotherapy. Semin Respir Crit Care Med 1997;18:545-54.
58. Gage AA, Baust J. Mechanisms of tissue injury in cryosurgery. Cryobiology 1998;37:171-86. [Crossref] [PubMed]
59. Marasso A, Gallo E, Massaglia GM, et al. Cryosurgery in bronchoscopic treatment of tracheobronchial stenosis. Indications, limits, personal experience. Chest 1993;103:472-4. [Crossref] [PubMed]
60. Mathur PN, Wolf KM, Busk MF, et al. Fiberoptic bronchoscopic cryotherapy in the management of tracheobronchial obstruction. Chest 1996;110:718-23. [Crossref] [PubMed]
61. Hetzel M, Hetzel J, Schumann C, et al. Cryorecanalization: a new approach for the immediate management of acute airway obstruction. J Thorac Cardiovasc Surg 2004;127:1427-31. [Crossref] [PubMed]
62. Schumann C, Hetzel M, Babiak AJ, et al. Endobronchial tumor debulking with a flexible cryoprobe for immediate treatment of malignant stenosis. J Thorac Cardiovasc Surg 2010;139:997-1000. [Crossref] [PubMed]
63. Johnston CM, Schoenfeld LP, Mysore JV, et al. Endoscopic spray cryotherapy: a new technique for mucosal ablation in the esophagus. Gastrointest Endosc 1999;50:86-92. [Crossref] [PubMed]
64. Browning R, Turner JF Jr, Parrish S. Spray cryotherapy (SCT): institutional evolution of techniques and clinical practice from early experience in the treatment of malignant airway disease. J Thorac Dis 2015;7:S405-14. [Crossref] [PubMed]
65. Jeong JH, Kim J, Choi CM, et al. Clinical Outcomes of Bronchoscopic Cryotherapy for Central Airway Obstruction in Adults: An 11-Years' Experience of a Single Center. J Korean Med Sci 2023;38:e244. [Crossref] [PubMed]
66. Chen TY, Goan YG, Tang EK, et al. Bronchoscopic cryosurgery for metastatic tumor causing central airway obstruction: A case report. Medicine (Baltimore) 2019;98:e14635. [Crossref] [PubMed]
67. Inaty H, Folch E, Berger R, et al. Unimodality and Multimodality Cryodebridement for Airway Obstruction. A Single-Center Experience with Safety and Efficacy. Ann Am Thorac Soc 2016;13:856-61. [Crossref] [PubMed]
68. Shea JM, Allen RP, Tharratt RS, et al. Survival of patients undergoing Nd:YAG laser therapy compared with Nd:YAG laser therapy and brachytherapy for malignant airway disease. Chest 1993;103:1028-31. [Crossref] [PubMed]
69. Klopp AH, Eapen GA, Komaki RR. Endobronchial brachytherapy: an effective option for palliation of malignant bronchial obstruction. Clin Lung Cancer 2006;8:203-7. [Crossref] [PubMed]
70. Villanueva AG, Lo TC, Beamis JF Jr. Endobronchial brachytherapy. Clin Chest Med 1995;16:445-54.
71. Roach M 3rd, Leidholdt EM Jr, Tatera BS, et al. Endobronchial radiation therapy (EBRT) in the management of lung cancer. Int J Radiat Oncol Biol Phys 1990;18:1449-54. [Crossref] [PubMed]
72. Chang LF, Horvath J, Peyton W, et al. High dose rate afterloading intraluminal brachytherapy in malignant airway obstruction of lung cancer. Int J Radiat Oncol Biol Phys 1994;28:589-96. [Crossref] [PubMed]
73. Lee JW, Lee JH, Kim HK, et al. The efficacy of external beam radiotherapy for airway obstruction in lung cancer patients. Cancer Res Treat 2015;47:189-96. [Crossref] [PubMed]
74. Escobar-Sacristán JA, Granda-Orive JI, Gutiérrez Jiménez T, et al. Endobronchial brachytherapy in the treatment of malignant lung tumours. Eur Respir J 2004;24:348-52. [Crossref] [PubMed]
75. Shaller BD, Filsoof D, Pineda JM, et al. Malignant Central Airway Obstruction: What's New? Semin Respir Crit Care Med 2022;43:512-29. [Crossref] [PubMed]
76. Acksteiner C, Steinke K. Percutaneous microwave ablation for early-stage non-small cell lung cancer (NSCLC) in the elderly: a promising outlook. J Med Imaging Radiat Oncol 2015;59:82-90. [Crossref] [PubMed]
77. Brace CL, Hinshaw JL, Laeseke PF, et al. Pulmonary thermal ablation: comparison of radiofrequency and microwave devices by using gross pathologic and CT findings in a swine model. Radiology 2009;251:705-11. [Crossref] [PubMed]
78. Senitko M, Oberg CL, Abraham GE, et al. Microwave Ablation for Malignant Central Airway Obstruction: A Pilot Study. Respiration 2022;101:666-74. [Crossref] [PubMed]
79. Kashiwabara K, Fujii S, Tsumura S, et al. Difference in the Overall Survival Between Malignant Central Airway Obstruction Patients Treated by Transbronchial Microwave Ablation and Stent Placement: A Single-institution Retrospective Study. Anticancer Res 2022;42:3125-31. [Crossref] [PubMed]
80. Nguyen DT, Vu NT, Dinh TTH. Massive lung necrosis due to microwave ablation in an octogenarian required urgent lobectomy. BMJ Case Rep 2022;15:e249610. [Crossref] [PubMed]
81. Montgomery WW. T-tube tracheal stent. Arch Otolaryngol 1965;82:320-1. [Crossref] [PubMed]
82. Freitag L, Tekolf E, Steveling H, et al. Management of malignant esophagotracheal fistulas with airway stenting and double stenting. Chest 1996;110:1155-60. [Crossref] [PubMed]
83. Oviatt PL, Stather DR, Michaud G, et al. Exercise capacity, lung function, and quality of life after interventional bronchoscopy. J Thorac Oncol 2011;6:38-42. [Crossref] [PubMed]
84. Bolliger CT. Airway stents. Semin Respir Crit Care Med 1997;18:563-70.
85. Ducic Y, Khalafi RS. Use of endoscopically placed expandable nitinol tracheal stents in the treatment of tracheal stenosis. Laryngoscope 1999;109:1130-3. [Crossref] [PubMed]
86. Mehta AC, Dasgupta A. Airway stents. Clin Chest Med 1999;20:139-51. [Crossref] [PubMed]
87. Miyazawa T, Yamakido M, Ikeda S, et al. Implantation of ultraflex nitinol stents in malignant tracheobronchial stenoses. Chest 2000;118:959-65. [Crossref] [PubMed]
88. Hauck RW, Lembeck RM, Emslander HP, et al. Implantation of Accuflex and Strecker stents in malignant bronchial stenoses by flexible bronchoscopy. Chest 1997;112:134-44. [Crossref] [PubMed]
89. Colt HG, Dumon JF. Airway stents. Present and future. Clin Chest Med 1995;16:465-78.
90. Lund ME, Force S. Airway stenting for patients with benign airway disease and the Food and Drug Administration advisory: a call for restraint. Chest 2007;132:1107-8. [Crossref] [PubMed]
91. Pertzov B, Gershman E, Izhakian S, et al. Placement of self-expanding metallic tracheobronchial Y stent with laryngeal mask airway using conscious sedation under fluoroscopic guidance. Thorac Cancer 2021;12:484-90. [Crossref] [PubMed]
92. Husain SA, Finch D, Ahmed M, et al. Long-term follow-up of ultraflex metallic stents in benign and malignant central airway obstruction. Ann Thorac Surg 2007;83:1251-6. [Crossref] [PubMed]
93. Shin JH, Kim SW, Shim TS, et al. Malignant tracheobronchial strictures: palliation with covered retrievable expandable nitinol stent. J Vasc Interv Radiol 2003;14:1525-34. [Crossref] [PubMed]
94. Profili S, Manca A, Feo CF, et al. Palliative airway stenting performed under radiological guidance and local anesthesia. Cardiovasc Intervent Radiol 2007;30:74-8. [Crossref] [PubMed]
95. Kim JH, Shin JH, Song HY, et al. Palliative treatment of inoperable malignant tracheobronchial obstruction: temporary stenting combined with radiation therapy and/or chemotherapy. AJR Am J Roentgenol 2009;193:W38-42. [Crossref] [PubMed]
96. Eapen GA, Shah AM, Lei X, et al. Complications, consequences, and practice patterns of endobronchial ultrasound-guided transbronchial needle aspiration: Results of the AQuIRE registry. Chest 2013;143:1044-53. [Crossref] [PubMed]
97. Dutau H, Di Palma F, Thibout Y, et al. Impact of Silicone Stent Placement in Symptomatic Airway Obstruction due to Non-Small Cell Lung Cancer - A French Multicenter Randomized Controlled Study: The SPOC Trial. Respiration 2020;99:344-52. [Crossref] [PubMed]
98. Dumon JF, Cavaliere S, Diaz-Jimenez JP, et al. Seven-year experience with the Dumon prosthesis. J Bronchology Interv Pulmonol 1996;3:6-10.
99. Kim JH, Shin JH, Song HY, et al. Use of a retrievable metallic stent internally coated with silicone to treat airway obstruction. J Vasc Interv Radiol 2008;19:1208-14. [Crossref] [PubMed]
100. Marchese R, Poidomani G, Palumbo VD, et al. Secondary Carina and Lobar Bronchi Stenting in Patients with Advanced Lung Cancer: Is It Worth the Effort? A Clinical Experience. Ann Thorac Cardiovasc Surg 2020;26:320-6. [Crossref] [PubMed]
101. Salguero BD, Joy G, Lo Cascio CM, et al. Normal Saline Versus Hypertonic Saline for Airway STENT Maintenance: SALTY STENT Study. J Bronchology Interv Pulmonol 2024;31:e0986. [Crossref] [PubMed]
102. Gildea TR, Young BP, Machuzak MS. Application of 3D Printing for Patient-Specific Silicone Stents: 1-Year Follow-Up on 2 Patients. Respiration 2018;96:488-94. [Crossref] [PubMed]
103. van Beelen S, Smesseim I, Guibert N, et al. Broadening the scope for three-dimensional printed airway stents. ERJ Open Res 2023;9:00673-2022. [Crossref] [PubMed]
104. Guibert N, Didier A, Moreno B, et al. Treatment of complex airway stenoses using patient-specific 3D-engineered stents: a proof-of-concept study. Thorax 2019;74:810-3. [Crossref] [PubMed]
105. Stehlik L, Hytych V, Letackova J, et al. Biodegradable polydioxanone stents in the treatment of adult patients with tracheal narrowing. BMC Pulm Med 2015;15:164. [Crossref] [PubMed]
106. van Pel R, Gan T, Daniels JMA, et al. Lung transplant airway complications treated with biodegradable airway stents: The Dutch multi-center experience. Clin Transplant 2024;38:e15289. [Crossref] [PubMed]