One of the most common problems in the general pulmonary clinic is the evaluation of patients with lung nodules. With the results of the soon-to-be-published National Lung Screening Trial suggesting a 20% reduction in mortality with the use of screening chest computed tomography (CT) in high-risk patients, the number of patients presenting with lung nodules is certainly going to increase. In this study, 27% of patients were found to have nodules >4 mm on the incident chest CT, and 95% of these nodules were benign (personal communication). When a patient presents with a lung nodule, it is important to determine the pretest probability that the nodule is benign or malignant. This depends on the patient's history (smoking, hemoptysis), the location of the nodule, and other radiographic characteristics (speculation, calcification, avidity on positron emission tomography scanning), etc. There are online tools available to assist the clinician with this Baysean approach (ie, www.chestx-ray.com). Nodules that have a high probability of malignancy, without evidence of metastatic disease, should likely be surgically removed, assuming the patient is a favorable surgical candidate. Similarly, nodules that are likely benign can be followed to ensure radiographic stability. If the nodule is located near the pleural surface, CT-guided transthoracic needle aspiration (TTNA) can yield a diagnosis in up to 80% of patients, although it may be associated with pneumothorax rates of 10% to 30%.1 Video-assisted thoracoscopic surgery can provide a definitive diagnosis in these patients, but is a more invasive procedure. The big question is how to manage nodules that have an intermediate pretest probability for malignancy, are found in high-risk patients, or are in a location that would require lobectomy/pneumonectomy to make a diagnosis. Unfortunately, bronchoscopy for peripheral nodules has been historically associated with a low overall diagnostic yield, especially in nodules <2 cm.2
Over the last several years, several technologies have improved the ability to bronchoscopically obtain tissue from parenchymal nodules. These include radial-probe endobronchial ultrasound and electromagnetic and virtual bronchoscopic navigation, with the greatest benefit likely resulting from a combination of technologies.3
In the last issue of the Journal of Bronchology and Interventional Pulmonology, Mahajan et al4 reviewed their use of electromagnetic navigation bronchoscopy (EMNB) using the superDimension system in 48 “high-risk” patients over a 2.5-year period. This was a well designed investigation, with definitions of true-positive and true-negative results being well defined. They reported a diagnostic yield of 77%, with a 22% false-negative rate. The average nodule size was larger in patients in whom a diagnosis was made (2.3 cm vs. 1.2 cm). It should be noted that these measurements were made in the anteroposterior diameter as opposed to the more commonly used largest overall diameter. Their rate of pneumothorax was 10%, which compares with the pneumothorax rate published in other studies of navigational bronchoscopy and is significantly lower than that obtained with TTNA.
One of the most important factors in predicting whether bronchoscopy can reach a nodule is the air-bronchus sign.5 Many parenchymal nodules are not located in an airway, and no matter how good the technology, it may be possible to get close to the lesion, but not to the lesion. It would have been interesting to see the percentage of patients in Mahajan et al4 study that had the air-bronchus sign. The authors sampled lesions with a combination of bronchoalveolar lavage, brushing, and transbronchial biopsy. Recent studies have suggested that adding peripheral transbronchial needle aspiration can significantly increase the yield of the procedure,6 and as it does not increase the complication rate, peripheral transbronchial needle aspiration should be used in all cases.
It is important to note that as 82% of the patients in whom EMNB was nondiagnostic were eventually diagnosed with malignancy, the prevalence of malignancy in this study population was quite high, and that disease prevalence is the single biggest determinant of the positive and negative likelihood ratios associated with test results. The authors reported a 35% rate of benign disease (true-negative for malignancy). This may be due in part to the higher prevalence of fungal disease in the mid-west United States, and their results may not be generalizable to geographic areas that have different disease prevalence rates.
It is crucial to understand that a “nondiagnostic” EMNB cannot be considered a “true negative,” unless appropriate clinical follow-up or additional tissue confirmation is obtained. In fact, this study by Mahajan et al4 is one of the only studies investigating navigational bronchoscopy where clinical follow-up was required to count the nondiagnostic result as a true-negative.
Mahajan et al4 study adds to the literature supporting the use of navigational bronchoscopy for peripheral pulmonary nodules. Future studies will hopefully directly compare each technology with standard bronchoscopy and TTNA, and the different technologies with each other, as these studies have not yet been performed.
1. Larscheid RC, Thorpe PE, Scott WJ. Percutaneous transthoracic needle aspiration biopsy: a comprehensive review of its current role in the diagnosis and treatment of lung tumors. Chest. 1998;114:704–709
2. Baaklini WA, Reinoso MA, Gorin AB, et al. Diagnostic yield of fiberoptic bronchoscopy in evaluating solitary pulmonary nodules. Chest. 2000;117:1049–1054
3. Eberhardt R, Anantham D, Ernst A, et al. Multimodality bronchoscopic diagnosis of peripheral lung lesions: a randomized controlled trial. Am J Respir Crit Care Med. 2007;176:36–41
4. Mahajan AK, Patel S, Hogarth DK, et al. Electromagnetic navigational bronchoscopy: an effective and safe approach to diagnose peripheral lung lesions unreachable by conventional bronchoscopy in high risk patients. J Bronchol Intervent Pulmonol. 2011;18:133–137
5. Seijo LM, de Torres JP, Lozano MaD, et al. Diagnostic yield of electromagnetic navigation bronchoscopy is highly dependent on the presence of a bronchus sign on CT imaging. Chest. 2010;138:1316–1321
6. Chao TY, Chien MT, Lie CH, et al. Endobronchial ultrasonography-guided transbronchial needle aspiration increases the diagnostic yield of peripheral pulmonary lesions: a randomized trial. Chest. 2009;136:229–236