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MMCTS
(October 18, 2007). doi:10.1510/mmcts.2006.002576 Copyright © 2007 European Association for Cardio-thoracic Surgery
Procedure Video-assisted mediastinoscopic lymphadenectomyDepartment of Thoracic Surgery, Katholisches Klinikum Koblenz, Kardinal-Krementz-Str. 1-5, 56073 Koblenz, Germany * Corresponding author: * Tel.: +49-261-496-9027; fax: +49-261-496-6469 b.witte{at}kk.koblenz.de
Systematic mediastinal lymphadenectomy is usually done at thoracotomy together with lung resection. It is a prerequisite for accurate nodal staging and has an impact on survival. With the introduction of neoadjuvant therapy for stage III lung carcinoma, mediastinal staging before therapy became more important. Video-assisted mediastinoscopic lymphadenectomy (VAMLA) is a minimally invasive technique of systematic mediastinal dissection that equals radicality of open lymphadenectomy, and can be carried out before neoadjuvant treatment and independently from tumour resection. The VAMLA dissection technique follows the anatomical mediastinal structures, and includes the stations 7, 4R+L, 2R+L, and 3. Compared to open dissection, VAMLA harvested significantly more nodes. Dissection rates of 96%, 92%, 100% and 100% for the stations 2R, 4R, 7 and 4L were reported. In routine clinical use, the mean duration was 54 min, the complication rate was 4.6%. Accuracy data in 130 patients with radiologically normal mediastinum were: sensitivity 93.8%, specificity 100%, false negative rate 0.9%. VAMLA is an extremely accurate staging tool as well as definitive mediastinal surgery. Thus, VAMLA is valuable if neoadjuvant therapy is considered for minor mediastinal involvement, to avoid re-mediastinoscopies after induction treatment, to define the exact involved radiation field in functionally unresectable patients, for highly accurate pre-therapy staging in trials, and to improve mediastinal dissection with VATS lobectomy and left-sided tumours.
Key Words: Lung carcinoma • Mediastinal lymphadenectomy • Mediastinal staging • Mediastinoscopy • Minimally invasive thoracic surgery • VAMLA • Video mediastinoscopy
VAMLA technique is based on bimanual dissection of clearly defined compartments along anatomical structures. VAMLA objectives are complete nodal dissection and avoidance of tumour spillage. Prerequisite for VAMLA is a two-bladed spreadable mediastinoscope [1], e.g. the Linder-Dahan videomediastinoscope (Photo 1). Spreading the blades creates a standard operation field of 32 mm. A spacer may add another 20 mm by lowering the lower blade. With this amount of exposure, bimanual dissection is possible. Useful instruments are a suction-coagulation device, a combined grasping and dissecting forceps, a clip applier, and a pair of scissors. VAMLA can be performed by one surgeon, if the scope is supported by a holder (Photo 2).
For the VAMLA dissection technique [1, 2], the mediastinum is divided into three compartments: central, right, and left (Table 1, Schematic 1). The central compartment comprises the subcarinal (station 7) and the upper part of the paraesophageal nodes (station 8). We consider station 7 as completely dissected, if 3 cm of each main bronchus are freed. All tissue below is defined as station 8. Dissection of station 8 is limited by the dimensions of the mediastinoscope. The right compartment is composed of the pretracheal, right paratracheal, and right tracheobronchial nodes (stations 2R and 4R on the Mountain Dresler map; 2R, 3 and 4R on the Naruke map). The left compartment consists of the left paratracheal and tracheobronchial nodes (stations 4L and 2L). From the central and right compartment, the adipose tissue containing lymph nodes is excised en bloc along the anatomical landmarks of the mediastinum. The left compartment is carefully dissected, and all visible nodes removed.
To protect the left recurrent nerve, en bloc resection on the left side is not advisable, as well as electrocautery. The same is true for 2 R+L nodes cranial of the innominate artery, where en bloc resection endangers both recurrent nerves. From the technical point of view, it is no problem to extend VAMLA to hilar nodes at the main bronchi and the intermediate bronchus. To minimize the risk of tumour spillage, the specimen should be handled with care to avoid fragmentation, tissue should be divided by coagulation whenever feasible to seal the resection margins, and irrigation should be generously used. Of course, VAMLA should not be carried out for extensive mediastinal disease or extranodal tumour growth.
Exposure of the trachea and insertion of the scope are similar to conventional mediastinoscopy (see Video 1). First, the central compartment is excised en bloc along both main bronchi, the pulmonary artery, and the esophagus (see Videos 2, 3, 4). Next, vena cava and pleura are exposed, and the pre- and right paratracheal fat pad is removed en bloc down to the azygos vein and right main bronchus (see Videos 5, 6, 7, 8). Then, the left recurrent nerve is identified, and left tracheobronchial and paratracheal adipose tissue is dissected, and all visible nodes removed (see Videos 9 and 10). Finally, the mediastinum is checked for complete dissection and haemorrhage and the skin closed without drainage.
Preliminary steps
En bloc resection of the central compartment The left bronchial artery coming up from behind the left main bronchus is often walled in by lymph nodes and has to be divided (Video 3). The caudal border of the subcarinal compartment to the paraesophageal station is not anatomically defined. For practical reasons, we dissect the medial margins of both main bronchi as long as 3 cm and consider all nodes in between as subcarinal nodes (Video 4).
En bloc resection of the right compartment From there the whole fat pad is taken down following the innominate vein, the vena cava, the right parietal pleura and the azygos vein (Videos 6,7,8).
Dissection of the left compartment
In a preliminary study of 40 patients [1], VAMLA dissection technique was standardized compared to open lymphadenectomy. VAMLA harvested significantly more nodes (20.7 vs. 14.3 nodes, P<0.0001). A study from the Hemer working group [3] focussed on dissected stations. Complete dissection rates of 96%, 92%, 100% and 100% for the stations 2R, 4R, 7 and 4L were reported. Their paper was the first to suggest a combination of VAMLA and VATS lobectomy. VAMLA feasibility and accuracy [4] was studied in 130 patients with lung carcinoma and radiologically normal mediastinum, who underwent VAMLA and consecutive lung resection with mediastinal reexploration. With a mean duration of 54 min (range, 30–150 min), VAMLA was considered to be feasible for routine pre-therapy workup. Morbidity was 4.6% (4 temporary left-sided recurrent nerve palsies, 1 mediastinitis, 1 chylothorax). Up to now, there has been observed no mortality, and no conversion to open surgery in more than 400 procedures. VAMLA remains highly accurate (sensitivity 93.8%, specificity 100%, false negative rate 0.9%) under routine clinical conditions.
The technical features of mediastinoscopy remained essentially unchanged since its introduction by Carlens in 1959. During the last decade, two significant technical modifications of the conventional mediastinoscope have changed mediastinoscopy forever. The idea of using a videocamera in mediastinoscopy by analogy with VATS is credited to Toni Lerut in 1989 [5]. The realization of this idea improved imaging of the mediastinal structures dramatically, and made mediastinoscopy more standardized, more user-friendly and more accessible to trainees. However, it was the development of a two-bladed spreadable video mediastinoscope by Linder and Dahan in 1992 that allowed increased exposure, bimanual dissection, and thus the development of new surgical techniques. Concurrent with technical progress in mediastinoscopy, neoadjuvant treatment of stage III lung cancer was introduced, and accuracy of pre-treatment mediastinal staging became more important. In this setting, development of a mediastinoscopic technique for complete mediastinal lymphadenectomy was the obvious thing to do. The extent and procedure of videomediastinoscopic lymph node dissection was designed to follow the principles of open systematic lymph node dissection: adherence to defined lymph node stations of the Naruke respectively Mountain Dresler maps, dissection along mediastinal anatomical structures, and en bloc resection whenever feasible [6]. Dissection of the left tracheobronchial and paratracheal lymph nodes should reasonably balance radicality and protection of the nearby left recurrent nerve. We prefer dissection and lymphadenectomy to en bloc resection of the left compartment. In contrast to open lymphadenectomy, most of VAMLA dissection is carried out with a combined suction-coagulation device. This device allows blunt and sharp dissection, coagulation and suction. Avoiding instrument changes, it simplifies and speeds up the procedure. Advantages of electric dissection and coagulation are sealing of small lymphatics, and a cytoxic effect on tumour cells. However, in the vicinity of the left recurrent nerve electric current is very likely to result in temporary palsy, and we cannot recommend its use in the whole left compartment. Electric dissection along vessels as the superior vena cava or the pulmonary artery requires careful application of a special low voltage current modification known as ‘soft coagulation’. As VAMLA was developed as a minimally-invasive version of systematic lymph node dissection, it is no surprise that its radicality and accuracy as well as its complication rate were found to be in the range of open lymphadenectomy. Thus, VAMLA can be considered as an extremely accurate staging tool as well as definitive mediastinal surgery. However, the curative value of VAMLA is not yet defined, and outcome, especially recurrence pattern of our VAMLA stage III patients is under investigation. Mediastinal nodes inaccessible to VAMLA, stations 5, 6, 8, 9, can be assessed by extended mediastinoscopy (station 5 and 6) during the same procedure [7], or an additional endoesophageal ultrasound-guided fine needle aspiration (EUS-FNA) [8, 9]. To complement VAMLA for assessment of resectability of central tumours, intraoperative mediastinal ultrasound (MUS) via the spreadable mediastinoscope was developed [10]. VAMLA has a specific profile of limitations, complications and contraindications. Working conditions are difficult in patients with extreme obesity, contracted cervical spine, intrathoracic struma, mediastinal scarring or fibrosis, and calcified or silicotic nodes. We see contraindications in patients with coagulopathies, severe cerebrovascular disease, and bulky disease or extranodal tumour growth. In patients with markedly enlarged nodes or bulky disease, endoscopic fine-needle aspiration techniques like EUS-FNA or endo-bronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) provide acceptable accuracy [8] and should, therefore, be the first step to obtain tissue specimen. Videomediastinoscopy or VAMLA are reserved for assessment of negative FNA results, or restaging after neoadjuvant treatment. This staged approach for extended mediastinal disease helps sparing some mediastinoscopies as well as remediastinoscopies [9]. For minor mediastinal disease, VAMLA provides definitive clearance of the mediastinum. Thus, re-mediastinoscopies after VAMLA and neoadjuvant treatment can be considered as unnecessary, and can be avoided, too. Whether and how to adopt VAMLA is worth some consideration [11]. On the whole, it is dependent on one's strategy for multimodality treatment of minor mediastinal disease, and lymphadenectomy with VATS lobectomy.Surgeons who feel comfortable with resection and adjuvant therapy of minor mediastinal disease, and systematic lymph node sampling with VATS lobectomy are very unlikely to adopt VAMLA. However, this widespread, pragmatic approach has several disadvantages:
The individual patient suitable for VAMLA should be fit for lung resection, have a technically respectable tumour, and normal lymph node size on CT scan. Contraindications against the VAMLA procedure and against neoadjuvant treatment should be observed. Occasionally, VAMLA is beneficial to non-resectable patients to define the smallest appropriate radiation field. In our experience, VAMLA is an extremely accurate staging tool as well as definitive mediastinal surgery, as its radicality can equal open lymphadenectomy. However, VAMLA is minimally invasive and therefore feasible before therapy. Thus, VAMLA is valuable, if neoadjuvant treatment is considered for any, even minor mediastinal involvement, to avoid remediastinoscopies after induction therapy, to define the exact involved radiation field in functionally unresectable patients, for highly accurate pre-therapy staging in trials, and to improve mediastinal dissection with VATS lobectomy and left-sided tumours.
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Surgical technique
