Virtual Library

Abstract not provided

Abstract:
Malignant central airway obstruction (mCAO) occurs in patients with lung cancer and in patients with pulmonary metastases from other malignancies, including thyroid, breast, renal cell, and colon(1). It is loosely defined as obstruction of >50% of the central airways(2). Malignant CAO results in dramatic alterations to quality of life (QOL), decreased functional status, bleeding, post-obstructive pneumonia, and a poor prognosis(3, 4). The principle goal in the management of mCAO is to restore airway patency, palliate, improve QOL and symptoms, spirometric values, and survival(1, 5-7). There are 3 classifications of mCAO: endobronchial, extrinsic, or mixed. Multiple ablative bronchoscopic tools are available to relieve endobronchial or mixed obstructions(8). Ablative techniques include lasers, electrocautery, argon plasma coagulation, photodynamic therapy, microdebriders, and cryotherapy(1). Stents are primarily used to treat patients with mixed and extrinsic airway obstruction(1). Lasers have no role in the management of extrinsic airway obstruction(9). Ost and colleagues(1) showed that among 26 physicians from 15 centers, performing over 1,100 procedures, there was significant practice pattern variability. They also report that there was no single best ablative technique with regard the primary goal of improvements in dyspnea or QOL. There are no large clinical trials comparing various ablative modalities head-to-head and thus, superiority of one technique over another remains undefined(3). However, all ablative techniques can be used alone or in combination(8). In order to obtain optimal treatment outcomes, physicians should be competent and versatile in the use of multiple complementary modalities. Herein, we provide a clinical review of lasers, a technique that delivers a non-contact heat energy by light via catheter(9, 10), in the management of mCAO. The effectiveness of lasers in achieving relief of obstruction and symptomatic improvement from mCAO in very large series established credibility of this modality(11). Although outcome data is limited, laser therapy appears to be effective in providing rapid relief of endobronchial obstruction with symptomatic improvement in 70-80%(9, 12-15). One-year survival following treatment was around 30%(9). Local disease recurrence with mCAO is typical unless tumor debulking is followed by adjunctive therapies(16). Several types of lasers exist and each use different media to generate light(10). The details and specific role of each laser is beyond the scope of this discussion. Special focus has been placed on the Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser because it has become the most frequently used nonsurgical technique in the management of malignant and benign endobronchial disorders(12, 13, 17-19). One significant advantage of the Nd:YAG laser is its balanced properties in its ability to photocoagulate or vaporize tumor and cut stenotic lesions. Its ability to photocoagulate and vaporize before mechanical debulking allows for improved control of hemorrhage in the airway during bronchoscopy(9, 10). Dumon et al. and Cavaliere et al were among the first to report their experience of the Nd:YAG laser in benign and mCAO(12, 13). Cavaliere and colleagues showed an improvement in airway lumen in 92% of patients with mCAO(12). In a follow up article, the largest series to date, radiographic improvement was noted in 93% of patients with bronchogenic carcinoma, and their overall complication rate was 2.3%(20). A disadvantage of the Nd:YAG laser is the associated considerable set-up, maintenance costs, and its bulky size. The power and distance of the fiber from the lesions as well as the ration of absorption and scattering coefficients of laser determine the tissue effect(10). Lower power or the farther the distance between the laser fiber and the lesion lead to a shallow effect and cause superficial tissue coagulation. Conversely, higher power settings or a shorter distance between the laser and lesion result in deeper penetration causing tissue carbonization and vaporization(10). Safety of Nd:YAG laser in airway procedures has been well established and with appropriate precautions, the safety record of laser therapy is excellent. Protective eyewear is mandatory when the laser beam is activated(17). A “timeout” should be performed to confirm that the fraction of inspired oxygen setting is <40%, which reduces the risk of airway fire. Literature suggests that complications can be minimized if particular attention is paid to keeping the power settings to less than 40W, pulse duration of 0.5-1 second, and always having the laser beam aimed parallel to the airway(9). Complete or nearly complete mCAO without adequate visualization of distal lumen is a relative contraindication due to a possible risk of perforation(4). Significant complications develop in fewer than 5% of cases. One study showed that in 7,000 laser treatments, the reported overall complication rate was 0.99%(16). Reported complications include marked fluctuations in oxygen saturations and end-tidal CO2, massive hemorrhage, airway perforation, pneumothorax, pneumomediastinum, airway fire, gas embolism, myocardial infarction, cardiac arrest, and death. Air embolism is a result of high flow of air coolant and contact probes. It is recommended that a non-contact mode be used while keeping the coaxial coolant air flow at a minimum level(21). Continuous suction is used during the procedure to remove smoke. Continuous inspection of the airways is performed to remove any debris and to optimize ventilation. Both rigid and flexible bronchoscopes are used successfully. With flexible bronchoscope, the lesion is either photocoagulated or carbonized prior to removal, or the whole lesion is vaporized(17). Flexible bronchoscope allows easier access to areas that may require acute angulation. Rigid bronchoscopy provides a wide operating channel allowing simultaneous use of multiple tools. Specifically, the patient can be ventilated, blood and secretions aspirated, and laser coagulation utilized. The aim is to devascularize the tumor and subsequently core out the tumor with the tip of the rigid bronchoscope(17). Additionally, mechanical sequential rigid bronchoscopic dilations can also be performed. When skilled in both techniques, the rigid technique is generally favored by many due to its multiple stated advantages(11, 13, 17, 22). However, in the absence of randomized controlled trials, expert opinion continues to guide therapeutic approaches. Most patients are managed in a multimodality fashion for the optimal outcome. Selection of a specific modality remains operator and institution specific. Irrespective of the type of ablative technique or choice of laser, the goal of treating mCAO remains the same, relieve the obstruction.

Abstract:
The fact that an early cancer is early in its nature implies that a curative therapy should be offered. However, radical treatments such as surgery and radiotherapy might not be the best options for various reasons. Firstly, the amount of normal tissue that has to be removed or denaturalized can contraindicate the treatment, secondly the unresectabilitiy for some central tumors, and finally the concern that metachronous lesions can occur and might need further intervention. Thus, the use of bronchoscopic therapies in the management of lung cancer limited to the airways has brought light to the management of early lung cancer. Several techniques are available to treat endoluminal superficial lesions, including laser, electrocautery, argon-plasma coagulation, photodynamic therapy, cryotherapy and brachytherapy. The curative potential of all these therapies has been demonstrated, as all of them are able to effectively destroy the depth of an early lung central cancer, which counts no more than 5 mm of malignant tissue. The definition of early lung cancer used in the studies of bronchoscopic therapies does not exactly correspond with the actual definitions of the TNM classification and differs among authors. Nagamoto et al. observed that squamous cell carcinoma (SCC) ≤ 3 mm thick and with longitudinal extension ˂ 20 mm was associated with no nodal involvement (1). Konaka et al. suggested that hypertrophic lesions of ˂ 1 cm are either carcinoma in-situ (CIS) or micro-invasive tumor within the muscle layer, while nodular and polypoid lesions ≥ 1 cm are more likely invasive beyond the cartilaginous layer (2). According to these, Mathur et al. defined early stage cancer as radiographically occult SCC that is endoscopically superficial, ˂ 2 cm in surface area with clearly visible margins and not invading beyond the bronchial cartilage (3). Later, the Japan Lung Cancer Society defined the bronchoscopic criteria of central type early stage lung cancer as that located subsegmental or more proximal, ˂ 2 cm with bronchoscopically recognizable margin and proven SCC (4). The new 8th edition of the TNM classification incorporates new definitions in the early stages including some special situations. Superficial spreading tumors in the central airways are those confined to the tracheal or bronchial wall regardless of size and location, and are labeled T1a ss. Carcinoma in situ (classified as Tis) now includes both squamous cell carcinoma in situ (SCIS, or squamous dysplasia) and adenocarcinoma in situ (AIS, which is localized, ≤ 3 cm and shows pure lepidic growth, lacking stromal, vascular, alveolar space or pleural invasion). Minimally invasive adenocarcinoma is classified as T1a(mi) and corresponds to solitary adenocarcinoma ≤ 3 cm with a predominantly lepidic pattern and ≤ 0.5 cm invasion. The invasive component is defined as histologic type other than lepidic or tumor cells infiltrating myofibroblastic stroma. In our setting, it is important to remark that examination of small biopsy specimens cannot exclude or quantify invasive components for AIS and T1a(mi) respectively. Although AIS can be highly suspected from biopsies with pure lepidic pattern together with a CT correlation of the ground glass component, AIS and T1a(mi) require examination of the entire resection specimen. The accuracy of the diagnostic techniques for early lung cancer represents the first step for defining the lesions suitable for endobronchial therapy. High definition bronchoscopy, autofluorescence bronchoscopy (AFB) and narrow band imaging (NBI) have been used for defining the margins of the lesion, the latter having a higher specificity. To evaluate the shallowness of the tumor, radial endobronchial ultrasound (rEBUS) and optical coherence tomography (OCT) have been used (6). Also, the combination of AFB and OCT have shown good results for both detection and characterization of premalignant lesions of the centrals airways (7). Thin-section CT (≤ 1 mm) and PET-CT might also be useful in the evaluation of premalignant lesions (8,9). Treatment success is directly dependent on lesion accessibility and the capability to correctly delineate the margins and shallowness of the lesions (10). Once the boundaries of the lesion are defined, choosing a technique over another depends mainly on the expertise of the bronchoscopist and availability of the therapy. Bibliography: 1. Nagamoto N, Saito Y, Ohta S, et al. Relationship of lymph node metastasis to primary tumor size and microscopic appearance of roentgenographically occult lung cancer. Am J Surg Pathol. 1989;13(12):1009-13. 2. Konaka C, Hirano T, Kato H, et al. Comparison of endoscopic features of early-stage squamous cell lung cancer and histological findings. Br J Cancer. 1999;80(9):1435-9. 3. Mathur PN, Edell E, Sutedja T, et al. Treatment of early stage non-small cell lung cancer. Chest. 2003;123(1 Suppl):176S-80S. 4. The Japan Lung Cancer Society Classification of Lung Cancer Kanehara. Tokyo. 2010. 5. Travis WD, Brambilla E, Nicholson AG, et al. The 2015 World Health Organization Classification of Lung Tumors. J Thorac Oncol. 2015;10:1243-60. 6. Kurimoto N, Murayama M, Yoshioka S, et al. Assessment of usefulness of endobronchial ultrasonography in determination of depth of tracheobronchial tumor invasion. Chest. 1999;115:1500-6. 7. Lam S, Standish B, Baldwin C, et al. In vivo optical coherence tomography imaging of preinvasive bronchial lesions. Clin Cancer Res. 2008;14:2006-11. 8. Sutedja TG, Codrington H, Risse EK, et al. Autofluorescence Bronchoscopy Improves Staging of Radiographically Occult Lung Cancer and Has an Impact on Therapeutic Strategy. Chest. 2001;120:1327-32. 9. Pasic A, Brokx HA, Comans EF, et al. Detection and staging of preinvasive lesions and occult lung cancer in the central airways with 18F-fluorodeoxyglucose positron emission tomography: a pilot study. Clin Cancer Res. 2005;11(17):6186-9. 10. 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 71-2 Figure 1 Figure 2 Endobronchial therapies for early lung cancer