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Noninvasive radiologic evaluation begins with a chest x-ray and chest CT scan through the adrenal glands to assess and determine the size of the lesion, involvement of surrounding structures, and overall resectability (Table 68-5). The sensitivity of CT scanning for detecting lung cancer is between 50% and 80%. MRI, once thought to hold promise as a diagnostic tool, is usually reserved for advanced anatomic problems when the results of CT scanning are ambiguous and for delineation of CNS metastases.36 PET scanning has high sensitivity (range: 79%–95%) for detecting lung cancers, particularly distant metastatic disease, but a lower specificity for disease determination. Integrated CT/PET is both sensitive and specific, yielding 98% correct tumor staging compared with final histopathologic staging. These technologies are expanding, but the instruments are expensive and not as widely available as CT.37 Although CT scanning remains the mainstay of clinical staging, CT scanning alone is inaccurate because it has a limited ability to determine mediastinal nodal involvement, chest wall invasion, mediastinal invasion, and malignancy of pleural effusions.37,38
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A number of staging and diagnostic procedures have evolved using bronchoscopy. Invasive bronchoscopic procedures include transbronchial needle aspiration, endobronchial ultrasound biopsy (EBUS-FNA), endoesophageal ultrasound fine-needle aspiration (EUS-FNA), and transbronchial and transesophageal needle biopsy. Although radiologic reconstructions of the bronchi and trachea are useful adjuncts to operative planning, bronchoscopy is recommended before every surgical resection as an aid to identifying anatomic abnormalities that might interfere with surgical resection and to confirm the accuracy of noninvasive study by determining the proximal extent of the tumor (i.e., distance from the carina). It is also valuable in identifying occult synchronous disease or anatomic variants of normal.
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Invasive preresectional surgical staging, pioneered by the Thoracic Surgical Group of Toronto, is routine practice in many centers.39,40 Mediastinal staging via mediastinoscopy was conceived originally to spare the morbidity of an exploratory thoracotomy.39 It is used presently to document the nodal metastatic extent of lung cancer before surgical resection, as a guide to therapeutic decision making, and for restaging lung cancer (see Chapter 70).41 Selective lymph node station sampling via cervical mediastinoscopy may identify patients with minimal N2 disease (stage III) for neoadjuvant chemotherapy or multimodality protocols (e.g., chemotherapy, radiotherapy, and surgery). Many predict that the role of mediastinal staging in lung cancer will expand with the increasing availability and application of new diagnostic and therapeutic techniques, such as tissue biopsy for biomarker staging42 and tissue typing for oncogenic mutations43 and drug-sensitivity testing.44
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Thoracoscopy is usually performed intraoperatively in patients who are identified with pleural effusions and for deep mediastinal nodal staging to confirm the presence or absence of cancer.
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Meta-analysis of multiple clinical staging trials has been used to demonstrate the superiority of pathologically over clinically staged lung cancer. Survival in clinically staged IB patients (T2N0 disease) was only 75% at 1 year and 40% at 5 years.45 In contrast, pathologically staged T2N0 disease yielded 90% survival at 1 year and 60% at 5 years,45 highlighting the limitations of current CT technology. Mediastinoscopy is the gold standard for mediastinal node staging preresection. Noninvasive techniques used to supplant mediastinoscopy for mediastinal nodal staging results in a 10% error regardless of the noninvasive technique used.
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Lesions located in specific lobes drain preferentially and predictably to specific nodal groups. Cervical mediastinoscopy is used to access nodes at the paratracheal levels (2R, 2L, 4R, 4L, 10R, and 10L) in addition to the subcarinal nodes at level 7. Anterior mediastinoscopy (also called parasternal mediastinoscopy) accesses lymph nodes at levels 5 and 6.
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Thoracoscopy of the right hemithorax accesses the right paratracheal nodes (level 4R), inferior pulmonary ligament nodes (level 9), and subcarinal nodes (level 7). In the left hemithorax, thoracoscopy is used to access the aortopulmonary window nodes (levels 5 and 6) and the posterior hilar nodes.
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Mediastinal staging by mediastinoscopy is commonly performed; it is also a safe and effective technique providing important histologic information with minimal morbidity. It is usually performed on an outpatient basis. It is currently indicated for patients with lung cancer suspected to have spread to the mediastinal nodes to provide accurate histologic lymph node staging and it is used to guide therapy. Patients not suspected of having mediastinal lymph node involvement may be staged with preoperative CT/PET and/or intraoperative thoracoscopic staging if appropriate to confirm the absence of mediastinal malignancy. The drawbacks to preresectional staging with mediastinoscopy are twofold: it requires general anesthesia and delays the surgical resection.