Bronchus Sign on CT Scan Rediscovered
2010; Elsevier BV; Volume: 138; Issue: 6 Linguagem: Inglês
10.1378/chest.10-0892
ISSN1931-3543
AutoresArmin Ernst, Devanand Anantham,
Tópico(s)Pleural and Pulmonary Diseases
ResumoIndeterminate peripheral lung lesions that are suspicious for malignancy are ideally treated by surgical resection.1Gould MK Fletcher J Iannettoni MD American College of Chest Physicians et al.Evaluation of patients with pulmonary nodules: when is it lung cancer? ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 108S-130SAbstract Full Text Full Text PDF PubMed Scopus (430) Google Scholar However, the high false-positive rate of CT scan, especially in lung cancer screening, suggests that in some cases a biopsy is appropriate.2Swensen SJ Jett JR Hartman TE et al.CT screening for lung cancer: five-year prospective experience.Radiology. 2005; 235: 259-265Crossref PubMed Scopus (569) Google Scholar The clinical suspicion of a benign diagnosis, high surgical risks that render the patient inoperable, and discordance between clinical judgment and imaging tests (eg, negative lesions in smokers on PET scans) are some indications for such a biopsy.1Gould MK Fletcher J Iannettoni MD American College of Chest Physicians et al.Evaluation of patients with pulmonary nodules: when is it lung cancer? ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 108S-130SAbstract Full Text Full Text PDF PubMed Scopus (430) Google Scholar A histologic diagnosis of malignancy is relevant even in patients who are nonsurgical candidates because of the availability of potentially curative external-beam radiation, stereotactic radiosurgery, and radiofrequency ablation.Traditionally, the role of bronchoscopy has been limited in parenchymal lung lesions without airway involvement because of poor diagnostic yields. This has been especially so in smaller, more peripheral nodules.3Rivera MP Mehta AC American College of Chest Physicians Initial diagnosis of lung cancer: ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 131S-148SAbstract Full Text Full Text PDF PubMed Scopus (360) Google Scholar In surgical candidates with solitary pulmonary lesions, routine bronchoscopy seldom changes either the indication for resection or the staging.4Torrington KG Kern JD The utility of fiberoptic bronchoscopy in the evaluation of the solitary pulmonary nodule.Chest. 1993; 104: 1021-1024Abstract Full Text Full Text PDF PubMed Scopus (113) Google ScholarElectromagnetic navigation, as described in the article by Seijo and colleagues5Seijo LM de Torres JP Lozano MD et al.Diagnostic yield of electromagnetic navigation bronchoscopy is highly dependent on the presence of a bronchus sign on CT imaging: results from a prospective study.Chest. 2010; 138: 1316-1321Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar in this issue of CHEST (see page 1316), attempts to improve the diagnostic yield of flexible bronchoscopy in such peripheral lung lesions. This system functions like a global positioning system within the patient's thorax, with a steerable probe that aims to enable the operator to navigate to lesions in the lung parenchyma beyond what is endoscopically visible. It remains but one of a number of emerging technologies in this field, and most literature to date consists of uncontrolled retrospective case series. Each step in the process of bronchoscopic lung biopsy has been targeted by these innovations: (1) preprocedure planning (eg, multiplanar CT scan reconstruction6Bandoh S Fujita J Tojo Y et al.Diagnostic accuracy and safety of flexible bronchoscopy with multiplanar reconstruction images and ultrafast Papanicolaou stain: evaluating solitary pulmonary nodules.Chest. 2003; 124: 1985-1992Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar), (2) endoscopic navigation (eg, electromagnetic navigation, virtual bronchoscopic navigation7Asano F Matsuno Y Shinagawa N et al.A virtual bronchoscopic navigation system for pulmonary peripheral lesions.Chest. 2006; 130: 559-566Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar), and (3) confirmation of localization (eg, radial probe endobronchial ultrasound,8Herth FJ Eberhardt R Becker HD Ernst A Endobronchial ultrasound-guided transbronchial lung biopsy in fluoroscopically invisible solitary pulmonary nodules: a prospective trial.Chest. 2006; 129: 147-150Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar CT scan fluoroscopy9Ost D Shah R Anasco E et al.A randomized trial of CT fluoroscopic-guided bronchoscopy vs conventional bronchoscopy in patients with suspected lung cancer.Chest. 2008; 134: 507-513Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). All of these modalities are attempting to obviate the need for transthoracic needle biopsies, which carry a well-documented, significant risk of pneumothoraces.10Ohno Y Hatabu H Takenaka D et al.CT-guided transthoracic needle aspiration biopsy of small (< or = 20 mm) solitary pulmonary nodules.AJR Am J Roentgenol. 2003; 180: 1665-1669Crossref PubMed Scopus (245) Google Scholar This risk of pneumothorax is further magnified in patients with obstructive spirometry, when multiple biopsy punctures are needed, and when the transthoracic needle-path length exceeds 40 mm.9Ost D Shah R Anasco E et al.A randomized trial of CT fluoroscopic-guided bronchoscopy vs conventional bronchoscopy in patients with suspected lung cancer.Chest. 2008; 134: 507-513Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar However, new bronchoscopic technology comes with incumbent high costs and steep learning curves. Therefore, it is critical to weed out modalities with only a marginal increment in diagnostic yield and select the right procedure for the right patients.Seijo et al5Seijo LM de Torres JP Lozano MD et al.Diagnostic yield of electromagnetic navigation bronchoscopy is highly dependent on the presence of a bronchus sign on CT imaging: results from a prospective study.Chest. 2010; 138: 1316-1321Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar present a well-done exploratory study involving 51 patients with pulmonary nodules who underwent electromagnetic navigation bronchoscopy without any fluoroscopic guidance. The precision of bronchoscopy is commendable, with a median registration variance of 4 mm and a navigation variance of 8 mm. This precision eliminated a potential confounder in diagnostic yield.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Both biopsy forceps and cytology needles were used, and rapid, onsite cytopathologic assessment was available. Using this protocol, the authors sought to identify the factors that account for the difference between the rate of successful navigation to lesions (>90%) and the positive diagnostic yield (60%-70%).11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar, 12Eberhardt R Anantham D Ernst A Feller-Kopman D Herth F Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial.Am J Respir Crit Care Med. 2007; 176: 36-41Crossref PubMed Scopus (424) Google Scholar A successful diagnosis in 79% of cases with a positive CT scan bronchus sign was found. This was significantly higher on multivariate analysis than cases without a bronchus sign (31%). Therefore, it was concluded that the presence of a positive CT scan bronchus sign could identify appropriate patients for electromagnetic navigation bronchoscopy and partially bridge the navigation-diagnosis gap.The authors have reaffirmed what is already known to be true for conventional transbronchial lung biopsies. The CT scan bronchus sign refers to the presence of a bronchus leading directly to a peripheral lung lesion. However, this relationship between the airways and tumors is not homogenous, and Tsuboi et al13Tsuboi E Ikeda S Tajima M Shimosato Y Ishikawa S Transbronchial biopsy smear for diagnosis of peripheral pulmonary carcinomas.Cancer. 1967; 20: 687-698Crossref PubMed Scopus (96) Google Scholar classified four variations: (1) bronchus patent up to the tumor and then cut off; (2) bronchus penetrating and contained within the tumor; (3) bronchus compressed by the tumor, with intact mucosa; and (4) bronchus constricted by perimucosal tumor spread, causing either smooth or irregular narrowing. The bronchus sign is not demonstrated in all lesions. It is identified more frequently in larger (>30 mm) nodules and in spiculated rather than smooth-bordered lesions.14Bilaçeroğlu S Kumcuoğlu Z Alper H et al.CT bronchus sign-guided bronchoscopic multiple diagnostic procedures in carcinomatous solitary pulmonary nodules and masses.Respiration. 1998; 65: 49-55Crossref PubMed Scopus (60) Google Scholar Appreciating these bronchus variations on CT scan has practical value because forceps biopsies have higher diagnostic yields in bronchus-cutoff lesions or bronchus-contained lesions, while transbronchial needle aspiration is more successful with bronchus-compressed lesions or bronchus-narrowed lesions.14Bilaçeroğlu S Kumcuoğlu Z Alper H et al.CT bronchus sign-guided bronchoscopic multiple diagnostic procedures in carcinomatous solitary pulmonary nodules and masses.Respiration. 1998; 65: 49-55Crossref PubMed Scopus (60) Google ScholarThe remaining unexplained gap between successful bronchoscopic navigation and a positive biopsy is likely to be explained by a host of technical factors. There are differences in lung volumes between the preprocedure planning CT scan that is taken in a single breath-hold at full inspiration compared with the spontaneously breathing patient during the bronchoscopy.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Some degree of navigation error may be inevitable, given the progressive-branching-and-narrowing nature of the airways.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Respiratory variations in the lower lobes due to diaphragmatic excursion as well as dislodgement of the extended working channel during the insertion of various biopsy instruments also compromise diagnostic yield.12Eberhardt R Anantham D Ernst A Feller-Kopman D Herth F Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial.Am J Respir Crit Care Med. 2007; 176: 36-41Crossref PubMed Scopus (424) Google ScholarUltimately, the main limitation of this technology is that it addresses only the navigation component of diagnosing peripheral lung lesions. Preprocedure planning (by analyzing the bronchus-tumor relationship) is an important additional step. However, in vivo confirmation of biopsy position using either biplane/CT scan fluoroscopy or endobronchial ultrasound needs to be addressed as well for a successful biopsy. The technical and logistical challenges of using such a combination of bronchoscopic modalities will then need to be weighed against diagnostic yield and complications.The aims in selecting any diagnostic modality for a particular patient are clear: maximize the diagnostic yield and avoid unnecessary tests. This translates to getting a positive histologic diagnosis without the need for either repeated or additional procedures. Attentive analysis of preprocedure radiologic imaging and a clear understanding of the limitations of the available diagnostic modalities are mandatory in deciding which procedure is recommended. Only then will patients truly reap the purported benefits of any advancement in bronchoscopic lung biopsy. Indeterminate peripheral lung lesions that are suspicious for malignancy are ideally treated by surgical resection.1Gould MK Fletcher J Iannettoni MD American College of Chest Physicians et al.Evaluation of patients with pulmonary nodules: when is it lung cancer? ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 108S-130SAbstract Full Text Full Text PDF PubMed Scopus (430) Google Scholar However, the high false-positive rate of CT scan, especially in lung cancer screening, suggests that in some cases a biopsy is appropriate.2Swensen SJ Jett JR Hartman TE et al.CT screening for lung cancer: five-year prospective experience.Radiology. 2005; 235: 259-265Crossref PubMed Scopus (569) Google Scholar The clinical suspicion of a benign diagnosis, high surgical risks that render the patient inoperable, and discordance between clinical judgment and imaging tests (eg, negative lesions in smokers on PET scans) are some indications for such a biopsy.1Gould MK Fletcher J Iannettoni MD American College of Chest Physicians et al.Evaluation of patients with pulmonary nodules: when is it lung cancer? ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 108S-130SAbstract Full Text Full Text PDF PubMed Scopus (430) Google Scholar A histologic diagnosis of malignancy is relevant even in patients who are nonsurgical candidates because of the availability of potentially curative external-beam radiation, stereotactic radiosurgery, and radiofrequency ablation. Traditionally, the role of bronchoscopy has been limited in parenchymal lung lesions without airway involvement because of poor diagnostic yields. This has been especially so in smaller, more peripheral nodules.3Rivera MP Mehta AC American College of Chest Physicians Initial diagnosis of lung cancer: ACCP evidence-based clinical practice guidelines (2nd edition).Chest. 2007; 132: 131S-148SAbstract Full Text Full Text PDF PubMed Scopus (360) Google Scholar In surgical candidates with solitary pulmonary lesions, routine bronchoscopy seldom changes either the indication for resection or the staging.4Torrington KG Kern JD The utility of fiberoptic bronchoscopy in the evaluation of the solitary pulmonary nodule.Chest. 1993; 104: 1021-1024Abstract Full Text Full Text PDF PubMed Scopus (113) Google Scholar Electromagnetic navigation, as described in the article by Seijo and colleagues5Seijo LM de Torres JP Lozano MD et al.Diagnostic yield of electromagnetic navigation bronchoscopy is highly dependent on the presence of a bronchus sign on CT imaging: results from a prospective study.Chest. 2010; 138: 1316-1321Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar in this issue of CHEST (see page 1316), attempts to improve the diagnostic yield of flexible bronchoscopy in such peripheral lung lesions. This system functions like a global positioning system within the patient's thorax, with a steerable probe that aims to enable the operator to navigate to lesions in the lung parenchyma beyond what is endoscopically visible. It remains but one of a number of emerging technologies in this field, and most literature to date consists of uncontrolled retrospective case series. Each step in the process of bronchoscopic lung biopsy has been targeted by these innovations: (1) preprocedure planning (eg, multiplanar CT scan reconstruction6Bandoh S Fujita J Tojo Y et al.Diagnostic accuracy and safety of flexible bronchoscopy with multiplanar reconstruction images and ultrafast Papanicolaou stain: evaluating solitary pulmonary nodules.Chest. 2003; 124: 1985-1992Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar), (2) endoscopic navigation (eg, electromagnetic navigation, virtual bronchoscopic navigation7Asano F Matsuno Y Shinagawa N et al.A virtual bronchoscopic navigation system for pulmonary peripheral lesions.Chest. 2006; 130: 559-566Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar), and (3) confirmation of localization (eg, radial probe endobronchial ultrasound,8Herth FJ Eberhardt R Becker HD Ernst A Endobronchial ultrasound-guided transbronchial lung biopsy in fluoroscopically invisible solitary pulmonary nodules: a prospective trial.Chest. 2006; 129: 147-150Abstract Full Text Full Text PDF PubMed Scopus (192) Google Scholar CT scan fluoroscopy9Ost D Shah R Anasco E et al.A randomized trial of CT fluoroscopic-guided bronchoscopy vs conventional bronchoscopy in patients with suspected lung cancer.Chest. 2008; 134: 507-513Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar). All of these modalities are attempting to obviate the need for transthoracic needle biopsies, which carry a well-documented, significant risk of pneumothoraces.10Ohno Y Hatabu H Takenaka D et al.CT-guided transthoracic needle aspiration biopsy of small (< or = 20 mm) solitary pulmonary nodules.AJR Am J Roentgenol. 2003; 180: 1665-1669Crossref PubMed Scopus (245) Google Scholar This risk of pneumothorax is further magnified in patients with obstructive spirometry, when multiple biopsy punctures are needed, and when the transthoracic needle-path length exceeds 40 mm.9Ost D Shah R Anasco E et al.A randomized trial of CT fluoroscopic-guided bronchoscopy vs conventional bronchoscopy in patients with suspected lung cancer.Chest. 2008; 134: 507-513Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar However, new bronchoscopic technology comes with incumbent high costs and steep learning curves. Therefore, it is critical to weed out modalities with only a marginal increment in diagnostic yield and select the right procedure for the right patients. Seijo et al5Seijo LM de Torres JP Lozano MD et al.Diagnostic yield of electromagnetic navigation bronchoscopy is highly dependent on the presence of a bronchus sign on CT imaging: results from a prospective study.Chest. 2010; 138: 1316-1321Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar present a well-done exploratory study involving 51 patients with pulmonary nodules who underwent electromagnetic navigation bronchoscopy without any fluoroscopic guidance. The precision of bronchoscopy is commendable, with a median registration variance of 4 mm and a navigation variance of 8 mm. This precision eliminated a potential confounder in diagnostic yield.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Both biopsy forceps and cytology needles were used, and rapid, onsite cytopathologic assessment was available. Using this protocol, the authors sought to identify the factors that account for the difference between the rate of successful navigation to lesions (>90%) and the positive diagnostic yield (60%-70%).11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar, 12Eberhardt R Anantham D Ernst A Feller-Kopman D Herth F Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial.Am J Respir Crit Care Med. 2007; 176: 36-41Crossref PubMed Scopus (424) Google Scholar A successful diagnosis in 79% of cases with a positive CT scan bronchus sign was found. This was significantly higher on multivariate analysis than cases without a bronchus sign (31%). Therefore, it was concluded that the presence of a positive CT scan bronchus sign could identify appropriate patients for electromagnetic navigation bronchoscopy and partially bridge the navigation-diagnosis gap. The authors have reaffirmed what is already known to be true for conventional transbronchial lung biopsies. The CT scan bronchus sign refers to the presence of a bronchus leading directly to a peripheral lung lesion. However, this relationship between the airways and tumors is not homogenous, and Tsuboi et al13Tsuboi E Ikeda S Tajima M Shimosato Y Ishikawa S Transbronchial biopsy smear for diagnosis of peripheral pulmonary carcinomas.Cancer. 1967; 20: 687-698Crossref PubMed Scopus (96) Google Scholar classified four variations: (1) bronchus patent up to the tumor and then cut off; (2) bronchus penetrating and contained within the tumor; (3) bronchus compressed by the tumor, with intact mucosa; and (4) bronchus constricted by perimucosal tumor spread, causing either smooth or irregular narrowing. The bronchus sign is not demonstrated in all lesions. It is identified more frequently in larger (>30 mm) nodules and in spiculated rather than smooth-bordered lesions.14Bilaçeroğlu S Kumcuoğlu Z Alper H et al.CT bronchus sign-guided bronchoscopic multiple diagnostic procedures in carcinomatous solitary pulmonary nodules and masses.Respiration. 1998; 65: 49-55Crossref PubMed Scopus (60) Google Scholar Appreciating these bronchus variations on CT scan has practical value because forceps biopsies have higher diagnostic yields in bronchus-cutoff lesions or bronchus-contained lesions, while transbronchial needle aspiration is more successful with bronchus-compressed lesions or bronchus-narrowed lesions.14Bilaçeroğlu S Kumcuoğlu Z Alper H et al.CT bronchus sign-guided bronchoscopic multiple diagnostic procedures in carcinomatous solitary pulmonary nodules and masses.Respiration. 1998; 65: 49-55Crossref PubMed Scopus (60) Google Scholar The remaining unexplained gap between successful bronchoscopic navigation and a positive biopsy is likely to be explained by a host of technical factors. There are differences in lung volumes between the preprocedure planning CT scan that is taken in a single breath-hold at full inspiration compared with the spontaneously breathing patient during the bronchoscopy.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Some degree of navigation error may be inevitable, given the progressive-branching-and-narrowing nature of the airways.11Makris D Scherpereel A Leroy S et al.Electromagnetic navigation diagnostic bronchoscopy for small peripheral lung lesions.Eur Respir J. 2007; 29: 1187-1192Crossref PubMed Scopus (196) Google Scholar Respiratory variations in the lower lobes due to diaphragmatic excursion as well as dislodgement of the extended working channel during the insertion of various biopsy instruments also compromise diagnostic yield.12Eberhardt R Anantham D Ernst A Feller-Kopman D Herth F Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial.Am J Respir Crit Care Med. 2007; 176: 36-41Crossref PubMed Scopus (424) Google Scholar Ultimately, the main limitation of this technology is that it addresses only the navigation component of diagnosing peripheral lung lesions. Preprocedure planning (by analyzing the bronchus-tumor relationship) is an important additional step. However, in vivo confirmation of biopsy position using either biplane/CT scan fluoroscopy or endobronchial ultrasound needs to be addressed as well for a successful biopsy. The technical and logistical challenges of using such a combination of bronchoscopic modalities will then need to be weighed against diagnostic yield and complications. The aims in selecting any diagnostic modality for a particular patient are clear: maximize the diagnostic yield and avoid unnecessary tests. This translates to getting a positive histologic diagnosis without the need for either repeated or additional procedures. Attentive analysis of preprocedure radiologic imaging and a clear understanding of the limitations of the available diagnostic modalities are mandatory in deciding which procedure is recommended. Only then will patients truly reap the purported benefits of any advancement in bronchoscopic lung biopsy.
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