новая папка / Operative Standards for Cancer Surgery Volume I 1st Edition

44R (includes right paratracheal nodes and pretracheal nodes extending to the left lateral border of trachea):

Upper border: the intersection of the caudal margin of the innominate vein with the trachea Lower border: the lower border of the azygos vein

4L (includes nodes to the left of the left lateral border of the trachea, medial to the ligamentum arteriosum): Upper border: the upper margin of the aortic arch Lower border: the upper rim of the left main pulmonary artery

6Includes lymph nodes anterior and lateral to the ascending aorta and aortic arch Upper border: a line tangential to the upper border of the aortic arch Lower border: the lower border of the aortic arch

What is the difference between MLND and MLNS, and what circumstances dictate the use of one or the other during an anatomic pulmonary resection for non-small cell lung cancer?

INTRODUCTION

In lung cancer patients, the presence of lymph node metastases is a significant prognostic factor for survival and helps inform treatment decisions. Therefore, accurate lymph node assessment during surgical resection for clinical early-stage lung cancer is essential. Although imaging modalities such as computed tomography and positron emission tomography are helpful in the preoperative assessment of lymph nodes, their ability to detect mediastinal lymph node metastases is limited. Given the false negative rate of cervical mediastinoscopy, mediastinal lymph node evaluation should be performed during pulmonary resection regardless of whether mediastinoscopy or endobronchial ultrasonography has already been performed and omitted only in extenuating circumstances. Visual inspection alone of the lymph nodes at the time of lung resection is also inadequate. Thus, the gold standard for lymph node assessment is complete excision and microscopic analysis of the lymph nodes.

The assessment of mediastinal lymph nodes during surgery for early-stage lung cancer can involve either a mediastinal lymph node dissection (MLND) or a less extensive mediastinal lymph node sampling (MLNS). The value placed on either approach varies among surgeons, and no study has definitively shown one approach to be associated with better outcomes. Advocates for MLND assert that removing occult nodal metastases may decrease recurrence and improve survival; detractors note that more than two-thirds of patients with N2 disease will have recurrence with distant metastases, regardless of the strategy used, and cite the increased time and potential complications associated with MLND. The purpose of this review is to (1) appropriately define MLND and MLNS and (2) provide the best evidence identifying the situations in which MLND should be performed.

METHODOLOGY

A flow chart illustrating the literature review is given in Figure 8-11. We conducted a Medline search of studies published from 1995 to 2013 using the Medical Subject Heading terms “mediastinal lymph node dissection” and “lung cancer surgery.” This search identified 1,052 articles. Filters were then applied to limit the search results to English language articles reporting clinical or comparative studies in humans for which abstracts were available. Of the 190 abstracts reviewed, 160 were excluded because they were case series or topic reviews, focused on metastatic disease to the

P.136 lung, or focused on mediastinoscopy or endobronchial ultrasonography. We carefully reviewed the remaining 30 articles and identified eight that evaluated MLND and systematic MLNS in similar populations (Table 8-2). The other 22 articles were excluded because they did not fulfill these criteria, focused on radical lymphadenectomy, or were secondary publications about series already included in the eight studies we identified.

FIGURE 8-11 Flow diagram for literature review process to address key question of MLND versus MLNS.

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TABLE 8-2 Summary of Studies Comparing Lymph Node Evaluation Strategies for Resectable Non-Small Cell Lung Cancer

MLND, mediastinal lymph node dissection; MLNS, mediastinal lymph node sampling; VATS, videoassisted thoracic surgery.

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FINDINGS

Definitions of Mediastinal Lymph Node Sampling and Mediastinal Lymph Node Dissection

MLND has been described as an en bloc resection of all midline and ipsilateral mediastinal lymph node basins

that leaves the trachea, phrenic nerves, aorta, and superior vena cava skeletonized.1,2,3 This resection includes lymph node stations 2R/4R, 7, 8R, and 9R on the right and stations 5/6, 7, 8L, and 9L on the left. The major technical challenge in performing this resection is identifying the structural borders of each station. For stations 2R/4R, these borders are the superior vena cava anteriorly, the trachea and right upper lobe bronchus medially, and the esophagus posteriorly. For station 7, the structural borders are the pericardium anteriorly, the carina and right mainstem bronchus/bronchus intermedius superiorly, and the esophagus posteriorly. Stations 8R and 9R lymph nodes should be resected as they are visualized during the mobilization of the inferior pulmonary ligament. On the left, stations 5/6 are bordered by the phrenic nerve anteriorly, the vagus/recurrent laryngeal nerve posteriorly, and the pulmonary artery and left mainstem bronchus inferiorly. Station 7 is bordered by the pericardium anteriorly, the esophagus posteriorly, and the left mainstem bronchus superiorly. Stations 8L and 9L are resected in the same manner as stations 8R and 9R.

Systematic MLNS, which has been defined as an exploration of each nodal station with biopsy of at least one

representative node from each station,2,4 is considered the minimum standard for lymph node evaluation during the surgical resection of earlystage lung cancer. In contrast to systematic MLNS, selective MLNS is vaguely defined, although it has been described as “cherry picking,” and involves the biopsy of only suspicious-looking lymph nodes. Selective MLNS has proven extremely limited in terms of providing adequate diagnostic and prognostic information and is no longer considered a reasonable option for the evaluation of the mediastinum in lung cancer patients.

Circumstances for Mediastinal Lymph Node Dissection or Mediastinal Lymph Node Sampling

In patients with non-small cell lung cancer (NSCLC), MLND or systematic MLNS should be performed at the time

of anatomic lung resection to facilitate accurate pathologic staging.3,5 However, the decision to perform MLND or systematic MLNS depends on a variety of factors. One such factor is the number of lymph nodes required to provide accurate pathologic staging. Studies have consistently shown that more lymph nodes are resected with

MLND than with MLNS; on average, MLND yields 17 or 18 lymph nodes, whereas systematic MLNS usually

yields approximately seven lymph nodes.6,7,8 Therefore, MLND should be performed in situations in which a high lymph node yield is required to better stage the disease or to completely excise potential N2 disease.

MLND does not improve the long-term survival of patients with T1 or T2 tumors and N0 disease proven by

systematic sampling at the time of anatomical lung resection.8 However, suspicious lymph nodes encountered at the time of pulmonary resection should be immediately evaluated by frozen section analysis, as the discovery of metastatic spread to the lymph nodes may change intraoperative management. In the setting of an intraoperatively confirmed metastatic lymph node, MLND is recommended.

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For patients with stage II (N1-positive) NSCLC, MLND is recommended and may improve survival.3 Although few studies have specifically compared outcomes following MLND to those following MLNS, several subgroup analyses have demonstrated that MLND offers a survival advantage over MLNS in patients with stage II lung

cancer.4,6,9,10

Surgical approach—thoracotomy, video-assisted thoracic surgery (VATS), or robot-assisted thoracic surgery— should not be a factor in deciding whether to perform MLND or systematic MLNS. However, whether an open approach or a minimally invasive approach offers a more thorough lymph node excision (by either MLND or MLNS) remains unclear. One study demonstrated that thoracotomy and minimally invasive approaches procure

equal numbers of lymph nodes.11 In contrast, another study found that the mean number of lymph nodes obtained with VATS (9.9 lymph nodes) was much lower than that obtained with open approaches (14.7 lymph

nodes).12 In addition, an analysis of the Society of Thoracic Surgeons General Thoracic Surgery Database demonstrated that compared with VATS, thoracotomy, owing to its higher rates of positive hilar lymph nodes, resulted in a higher rate of cancer upstaging in patients with clinical stage I lung cancer. This difference

disappeared, however, among patients treated by surgeons who predominately used VATS.13 Compared with systematic MLNS, MLND has been associated with small but clinically insignificant increases in operative time, blood loss volume, and chest tube drainage volume. In experienced centers, therefore, MLND adds minimal morbidity compared to systematic MLNS.

CONCLUSION

The key difference between MLND and systematic MLNS is that MLND removes more lymph nodes than MLNS does. For patients with suspected or documented stage II (N1 or T3) lung cancer, MLND should be performed to improve staging and long-term survival regardless of the surgical approach employed.

REFERENCES

1.Martini N. Mediastinal lymph node dissection for lung cancer. The Memorial experience. Chest Surg Clin N Am 1995;5(2):189-203.

2.Allen MS, Darling GE, Pechet TT, et al; ACOSOG Z0030 Study Group. Morbidity and mortality of major pulmonary resections in patients with early-stage lung cancer: initial results of the randomized, prospective ACOSOG Z0030 trial. Ann Thorac Surg 2006;81(3):1013-1019; discussion 1019-1020.

3.Lardinois D, De Leyn P, Van Schil P, et al. ESTS guidelines for intraoperative lymph node staging in non-

small cell lung cancer. Eur J Cardiothorac Surg 2006;30(5):787-792.

4. Keller SM, Adak S, Wagner H, et al. Mediastinal lymph node dissection improves survival in patients with stages II and IIIa non-small cell lung cancer. Eastern Cooperative Oncology Group. Ann Thorac Surg

2000;70(2):358-365.

5.Howington JA, Blum MG, Chang AC, et al. Treatment of stage I and II non-small cell lung cancer: diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2013;143(5)(suppl):e278S-e313S.

6.Lardinois D, Suter H, Hakki H, et al. Morbidity, survival, and site of recurrence after mediastinal lymphnode dissection versus systematic sampling after complete resection for non-small cell lung cancer. Ann Thorac Surg 2005;80(1):268-274.

7.Doddoli C, Aragon A, Barlesi F, et al. Does the extent of lymph node dissection influence outcome in patients with stage I non-small-cell lung cancer? Eur J Cardiothorac Surg 2005;27(4):680-685.

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8.Darling GE, Allen MS, Decker PA, et al. Randomized trial of mediastinal lymph node sampling versus complete lymphadenectomy during pulmonary resection in the patient with N0 or N1 (less than hilar) nonsmall cell carcinoma: results of the American College of Surgery Oncology Group Z0030 Trial. J Thorac Cardiovasc Surg 2011;141(3):662-670.

9.Izbicki JR, Passlick B, Pantel K, et al. Effectiveness of radical systematic mediastinal lymphadenectomy in patients with resectable non-small cell lung cancer: results of a prospective randomized trial. Ann Surg

1998;227(1):138-144.

10.Wu Y, Huang ZF, Wang SY, et al. A randomized trial of systematic nodal dissection in resectable nonsmall cell lung cancer. Lung Cancer 2002;36(1):1-6.

11.Watanabe A, Koyanagi T, Obama T, et al. Assessment of node dissection for clinical stage I primary lung cancer by VATS. Eur J Cardiothorac Surg 2005;27(5):745-752.

12.Merritt RE, Hoang CD, Shrager JB. Lymph node evaluation achieved by open lobectomy compared with thoracoscopic lobectomy for N0 lung cancer. Ann Thorac Surg 2013;96(4):1171-1177.

13.Boffa DJ, Kosinski AS, Paul S, et al. Lymph node evaluation by open or video-assisted approaches in 11,500 anatomic lung cancer resections. Ann Thorac Surg 2012;94(2):347-353.