Techniques for Staging and Restaging of Lung Cancer




Introduction



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Lung cancer is the leading cause of cancer death in the United States in both men and women. In 2011, there were an estimated 221,000 new cases of lung cancer and 156,900 estimated deaths owing to the disease.1 When indicated, surgery is the most effective curative therapy for lung cancer. For patients with limited non–small-cell lung cancer (NSCLC), lung resection remains the therapy of choice, offering the greatest potential for cure and long-term survival. Surgery also may play a limited role in small-cell lung cancer. However, of patients who present initially with lung cancer, 55% have distant metastatic disease, 30% have disease spread to regional lymph nodes, and only 15% have disease confined to the lung.2 Thus, accurate staging in lung cancer is an essential component of management and prognosis.



After primary tumor diagnosis, in addition to evaluating for distant spread and assessing lung reserve and comorbidities, evaluation of the mediastinum and mediastinal lymph nodes is vital to defining tumor stage and subsequent surgical planning. Despite advances in technology, mediastinoscopy remains an important tool for the thoracic surgeon in the staging of bronchogenic carcinoma, as well as in the diagnosis of disease in the mediastinum, as described in Chapter 156.



Originally described by Carlens in 1959,3 mediastinoscopy has been the subject of a number of studies. It has been shown to be a safe procedure, with morbidity rates between 0.6% and 3.7% and mortality rates ranging from 0% to 3% in several large series.4 In comparison with noninvasive diagnostic procedures, such as CT scanning and MRI, studies have shown a sensitivity for cervical mediastinoscopy ranging from 0.44 to 0.92.5 Specificities and positive predictive values of 1.00 have been described, but this is often secondary to the study design, with reference made to findings during mediastinoscopy, rather than actual disease at various lymph node stations. Although mediastinoscopy is currently the “gold standard” for assessing lymph node status (its negative predictive value is >90%), this chapter also addresses other existing and emerging imaging modalities that can be used to augment staging accuracy. The indications and contraindications to cervical mediastinoscopy are outlined in Table 70-1.




Table 70-1Indications and Contraindications for Mediastinoscopy




Preoperative Assessment



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Chest x-ray, chest CT scan, pulmonary function tests, and appropriate medical optimization are performed before mediastinoscopy and major lung resection. Although most surgeons prefer to delay the definitive pulmonary resection until final pathology is available from the mediastinoscopy, some perform mediastinoscopy in the setting of definitive resection if the frozen-section results are negative for metastatic tumor.




Preoperative Pet Imaging



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Although mediastinoscopy/otomy has the distinct advantage of providing direct visualization of suspicious mediastinal nodal disease, as well as a tissue diagnosis of such nodes, other studies are available in the preoperative staging repertoire. A noninvasive imaging modality currently in clinical use to evaluate for hilar, mediastinal, and extrathoracic metastases is positron-emission tomography (PET). By using the radioisotope [18F]fluorodeoxyglucose (FDG) to detect metabolically overactive cellular growth, one can more accurately describe a patient’s clinical stage and appropriate therapeutic maneuvers.



There is currently no absolute indication for the use of PET scanning, although some guidelines do exist in the literature. It seems clear that for patients who display clear evidence of extrathoracic disease, PET scanning is a costly and unnecessary test that will not change clinical management. Generally, a PET scan is indicated for patients with a question of extrathoracic metastases, those with questionable clinical stage III (cIII) disease (and even cI and cII disease), because surgical management may be altered in at least 8% to 18% of these patients.6,7



The data to support these clinical recommendations are substantial. PET scans, when compared with CT scans of the chest, abdomen, and pelvic anatomy, have an increased sensitivity for detecting disease, ranging from 79% to 95% versus 50% to 86% for CT.810 The significance of this is most noticeable in light of evidence that 7.5%, 18%, and 24% of patients with cI, cII, and cIII disease, respectively, will have extrathoracic disease by PET scanning and hence may avoid an unnecessary nontherapeutic resection.11 The strengths of PET scanning lie in its superior sensitivity and accuracy (>90%).12 This has led many to provide recommendations about continued operative staging (i.e., mediastinoscopy) depending on PET and CT scanning. Surgical staging may not be necessary in patients with negative CT and PET,13 negative PET and mediastinal nodes less than 1.5 cm,14 or if the primary lesion has a PET standardized uptake value (SUV) of less than 2.5 and a negative mediastinum.15



Although it has excellent sensitivity, the specificity of PET scanning is unacceptably low. A number of inflammatory and infectious conditions can produce a positive PET scan in the absence of malignancy, thus leading to either unnecessary operative diagnostic procedures or, worse yet, a decision to forego definitive treatment because of a false assumption of metastatic disease (overstaging). This is critical because there are data to suggest that even minimal N2 disease (e.g., ipsilateral mediastinal nodal metastases) can be resected with a primary tumor for a 5-year survival rate of 40% compared with 8% for bulky N2 disease.11 In addition, since several studies have demonstrated high false-negative and false-positive rates (11%–33% and 15%–52%, respectively, with PET), surgical staging continues to be an important part of the preoperative workup.



Endobronchial Ultrasound and Endoscopic Esophageal Ultrasound in Mediastinal Staging


The introduction of endobronchial ultrasound (EBUS) and endoscopic esophageal ultrasound (EUS) has aided clinicians in determining appropriate candidates for surgical versus nonoperative therapy for lung cancer in a less invasive manner. Endobronchial ultrasound with transbronchial FNA (EBUS-TBNA) can be used to biopsy lymph nodes in stations 1 to 4, 7, and 10 to 12. Accuracy rates of over 90% have been reported by the combined use of EBUS and EUS-FNA biopsy to stage the mediastinum in NSCLC.16



To describe the technique of EUS briefly, an endoscope is inserted into the esophagus with sonographic examination of nodal tissue distributed around the esophagus. By passing the endoscope distally, one can assess adrenal lesions and, more frequently, posterior mediastinal lymph nodes, most notably stations 7, 8, and 9. Level 5 nodes in the aortopulmonary window can be accessed, as well as occasionally the levels 2 and 4 paratracheal nodes. In contrast with PET, nodes as small as 3 mm can be visualized, and those 5 mm or larger may be biopsied.17 The only inaccessible mediastinal nodes are those anterior to the tracheobronchial tree (levels 2, 3, and 4) because air within the proximal airway distorts ultrasound findings.



EUS with FNA has gained considerable acceptance as an adjunct to mediastinoscopy, particularly in evaluating posterior mediastinal nodes at levels 5, 7, 8, and 9. Recent data suggest that EUS with FNA is superior to any other technique in investigating the posterior mediastinum, with sensitivity of 84% to 94%, specificity of 100%, and accuracy of 94% to 98% in determining regional disease.1821



Some have advocated the use of EBUS-TBNA and EUS-FNA as a primary method of staging the mediastinum. This method can be supported by its minimally invasive approach and relatively low risk, coupled with its ability to provide accurate, thorough information about locoregional and distant disease. A randomized controlled multicenter trial assigned 241 patients to either surgical staging alone or combined EBUS-TBNA and EUS-FNA followed by surgical staging if no nodal metastases were found. For patients without evidence of mediastinal metastases following surgical staging in either group, a thoracotomy with complete lymph node dissection was done. This study found that EBUS-TBNA and EUS-FNA improved the detection of nodal metastases and reduced the number of unnecessary thoracotomies by more than half compared with surgical staging alone.22 In a recent prospective trial, EBUS-TBNA and mediastinoscopy were performed in the same setting in 153 patients, and thoracotomy with pulmonary resection and mediastinal lymphadenectomy were performed on those patients for whom no evidence of N2 or N3 disease was found on EBUS-TBNA or mediastinoscopy.23 EBUS-TBNA was found to have no statistical difference in sensitivity, negative predictive value, and diagnostic accuracy compared to mediastinoscopy.24 In fact, such data are so encouraging that some centers have suggested replacing mediastinoscopy with EBUS-TBNA and EUS-FNA as the “gold standard” for staging the mediastinum.



Enthusiasm for EBUS/EUS used either alone or in conjunction with currently accepted surgical staging techniques must be tempered by a number of factors. Much of the current data supporting EBUS/EUS has been compiled at advanced tertiary care centers with significant experience in the technique. The assessment of tissue (mediastinoscopy) versus cytology (EBUS/EUS) also may factor into the accuracy of detecting micrometastases, as well as the ability to provide adequate tissue for tumor marker and mutation analysis.




Cervical Mediastinoscopy Technique



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Preparation


General anesthesia is induced with a single-lumen endotracheal tube. The patient is positioned supine on the OR table with the occiput of the head at the top of the table. The neck is maximally extended with the aid of an interscapular roll. The back is elevated to 20 to 30 degrees in a reverse Trendelenburg position. The headboard can be lowered to aid in extension, permitting direct access to the suprasternal notch. The endotracheal tube is positioned laterally, away from the operating hand of the surgeon and the mediastinoscope. The table generally is rotated 90 degrees away from the anesthetist. The anterior chest and neck are fully prepped and draped in the event that emergent sternotomy is necessary. Placing a right radial arterial line can be helpful for monitoring, especially dampening of the arterial waveform, which may indicate innominate artery compression.



Technique


A 3-cm incision is made in the midline one fingerbreadth above the sternal notch (Fig. 70-1A). The incision is carried down through the platysma. The midline then is opened vertically between the two layers of strap muscles until the trachea is exposed. Occasionally, the thyroid isthmus needs to be retracted cephalad or even divided to aid in exposure. Rarely, the thyroid artery, internal mammary artery, or branch of the inferior thyroid artery needs to be ligated. The anterior trachea is exposed, and the pretracheal fascia is incised and elevated. A pretracheal tunnel is fashioned with blunt dissection with the index finger (Fig. 70-1B). During the dissection, the dorsal aspect of the finger remains on the trachea, whereas the volar aspect comes in contact with the innominate artery (Fig. 70-1C). A side-to-side sweeping motion is made with the finger to clear the pre- and paratracheal spaces. The mediastinoscope is introduced into the pretracheal tunnel with constant traction anteriorly and a slow rotating motion during the dissection (Fig. 70-2). Care is taken to avoid forcing the scope at any time. Further blunt dissection is performed with a blunt metal suction device.

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Dec 30, 2018 | Posted by in VASCULAR SURGERY | Comments Off on Techniques for Staging and Restaging of Lung Cancer
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