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(June 19, 2007). doi:10.1510/mmcts.2005.001818 Copyright © 2007 European Association for Cardio-thoracic Surgery Procedure Conventional resection of pulmonary metastasesMayo Clinic Rochester, Department of General Thoracic Surgery, 200 First Street SW, Rochester, MN 55901, USA * Corresponding author: * Tel.: +1-507-255 5123; fax: +1-507-255 6203 claude.deschamps{at}mayo.edu
We present an overview of surgical technique for the resection of secondary tumor metastases to the lungs. Issues addressed include the optimal surgical approach, the requirement to remove all lesions while preserving unaffected lung parenchyma and the advantages of the available surgical staplers and devices. In selected patients, resection of metastatic lesions to the lung or chest wall offers a survival benefit. Although pulmonary metastases without further tumor spread may represent unique host or tumor biology, approximately 40% of patients survive 5 years. As it is not uncommon to repeat metastasectomy, consideration of technical aspects is important.
Key Words: Metastasectomy • Pulmonary • VATS
Metastasectomy was initially described in 1882 for a chest wall sarcoma [1]. Secondary lesions from almost all primary tumors have been resected. However, colon, renal and sarcomatous metastatic lesions are the most common. Operative approach includes thoracotomy, video assisted thoracoscopy (VATS), sternotomy and clamshell incision. For bilateral metastases, sternotomy, clamshell incision, bilateral anterior thoracotomies or interval thoracotomy/VATS can be performed.
Thoracotomy The lung and pleural surfaces are grossly inspected and the inferior pulmonary ligament divided. Any adhesions should be cauterized to fully mobilize the lung. With the assistant holding each lobe up with a lung clamp (Duval retractor) the surgeon carefully palpates the lung parenchyma (Schematic 1).
Lesions may be marked with the electrocautery as this facilitates the planning of resection lines, and it may be desirable to include more than one lesion in a target area for resection. Usually the gastrointestinal anastomotic (GIA) linear stapler is used to resect the lesion, as this will reduce air leak and is usually hemostatic (Schematic 2). Care should be taken to ensure the stapler affords a reasonable resection margin (0.5–1 cm). However, there is no benefit of an excessive resection margin, as the possibility of further resections makes lung preservation an important issue. CT of a typical lesion resected (along with others) at thoracotomy is shown in Photo 1.
Occasionally the position of the lesion is difficult to resect with the GIA stapler. Because of a suboptimal angle its use may lead to inclusion of excess normal lung within the staple line. Here consideration can be given to the use of a thoracic anastomotic (TA) staple gun. This is also useful, especially if a broad base of tissue remains (Photo 2). Alternatively, the endo GIA gun inserted through the planned port for the chest tube may provide a better angle. Endoscopic staplers with hinged joints may also be used to obtain the optimal resection line.
All staple lines should be checked for hemostasis. Smaller areas can be electrocauterized while larger areas may have to be oversewn with a 3.0 prolene suture. Where mediastinal nodes are enlarged on CT these can be sampled either at VATS or thoracotomy. In the presence of adenocarcinoma pathological diagnostic confirmation of mediastinal nodes may offer staging and prognostic information [2]. The paratracheal nodes can be found by incising the pleura in front of the trachea, followed by blunt or sharp dissection to mobilize a node for biopsy. On the left, the five and six nodes can be directly visualized after retracting the lung inferiorly. The subcarinal nodes are visualized by retracting the lung anteriorly, followed by blunt or sharp dissection. The inferior pulmonary ligament nodes are found by retracting the lung superiorly.
Central/hilar lesions or lesions close to main blood vessels
Deep lesions Lesions that are deep within the lung parenchyma may not be amenable to a stapled resection. It may be helpful to dissect out the fissures to allow the stapler to get around the lesion. Larger lesions may be best treated by anatomical resection. For smaller lesions, targeted electrocautery wedge excision with a surrounding margin may be performed. Large vessels may be clipped or tied. Once excised the remaining lung surfaces are opposed with a running 3.0 prolene suture in two layers (Schematic 3).
Pneumonectomy Generally this is not advised, however, in highly selected cases, and where lesser resection is not possible for anatomical reasons this may be justified (Photo 4).
Resection of adjacent structures This is appropriate in selected cases where the lesion invades resectable adjacent structures such as chest wall, diaphragm and pericardium (Photo 5).
Video assisted thoracoscopy (VATS) In patients who have a small number of peripheral lesions VATS may spare the morbidity of a thoracotomy. Usually, however, more lesions are found at thoracotomy than seen on the CT scan and this would be less likely to happen with VATS. Once again the CT chest should be carefully examined to identify the target lesions. The scapular tip may be used as a reference point as it will be helpful to know where to focus palpation for lesions that are not surface visible (Photo 6).
A double lumen tube is placed and the patient positioned in the lateral decubitus position. The camera port is inserted in the anterior axillary line in approximately the 10th intercostal space. Positioning of the other two ports may be targeted along the line of a thoracotomy incision should it become necessary to convert (Photo 6). Alternatively a port may be placed closer to where the lesion is expected to facilitate palpation. Occasionally a lesion may be visible on the surface and the pleural and lung surfaces should be inspected. Adhesions are cauterized to completely free the lung. This mobility will allow the lung surface to be brought up to a palpating finger. Photos 7 and 8 show CT images of lesions excised by VATS. The resection of the lesions seen in Photo 7 is shown on Video 1.
Video 2 shows resection of the metastasis with endoscopic linear stapler (normal thickness or blue staple load) and Video 3 shows removal of the specimen from the chest cavity, within a sterile surgical glove.
At VATS, use may be made of anatomical fissure lines to minimize the number of staple lines (Photo 9).
More than one instrument may be inserted in a port site. To prevent removal of excessive amounts of tissue a clamp can be passed along side the camera to retract unwanted normal lung out of the stapler. To minimize the risk of port site recurrence the specimen should be withdrawn within a collection device. While there are tissue catchers available commercially, we advocate the use of a surgeon's glove, grasped by two curved clamps (Video 1). The glove is first passed through the port by the assistant and without crossing the clamps the opening is shown to the surgeon. Once in, the specimen can be withdrawn within the glove. Port sites are then closed in layers after the positioning of 1 size 32 apical chest tube.
Sternotomy
Bilateral anterior thoracotomies This approach, popularized for double lung transplantation allows for bilateral chest exploration in the supine position without the need for turning the patient during the operation. It has most of the benefits of sternotomy but allows better access to the hilum, fissure and posterior chest, as in a conventional posterolateral thoracotomy. With double lumen intubation a submammary incision is made and the chest entered over the top of the 4th rib. The chest cavity and lungs are inspected and palpated in the usual fashion. If further exposure is required a clamshell incision can be created by transection of the sternum and ligation of the internal mammary arteries. Metastasectomy proceeds exactly as described above for sternotomy and thoracotomy.
Clamshell incision
Autopsy studies show that approximately 1/3 of cancer patients die with lung metastasis. In some patients disease is confined solely to the lungs, especially with sarcoma [3]. Hence a minority cohort exists for whom metastasectomy may prolong survival. Preoperative requirements include control of the primary site and the absence of widespread metastasis elsewhere. The exception to this would be a colorectal primary with resectable hepatic and pulmonary metastases. Pulmonary metastasectomy is generally well tolerated with low morbidity and mortality [4]. After complete resection 5-, 10- and 15-year survival rates were 36%, 26% and 22%, respectively, for all types of metastases. For incomplete resection survival was only 13% at 5 years and 7% at 10 years [4]. Metastasectomy for germ cell tumors had the best survival with 68% and 63% alive at 5 and 10 years, respectively. Melanoma was worst with 21% and 14% at 5 and 10 years. Results for colorectal, breast and kidney generally mirrored the overall results with 5- and 10-year survival of 37–41% and 21–24%, respectively. Potential favorable prognostic factors include the disease free interval (DFI), R0 resection with complete disease clearance, tumor doubling time (TDT), number of metastases and other tumor specific factors such as carcinoembryonic antigen for colorectal cancer, hormone receptors for breast cancer and beta HCG in teratoma [4,5,6]. The most consistent predictor is the DFI although not all studies support this [7]. Survival results to a large extent reflect the overall behavior and prognosis of the primary tumor and unique host biology. It is generally acknowledged that there is a survival benefit favoring metastasectomy (as opposed to no surgery or chemoradiotherapy only) for colon cancer, sarcoma [3] and renal cell [5]. The benefit is more controversial for patients with breast cancer in whom pulmonary metastases are thought to represent systemic disease. Metastasectomy is considered to be adjunctive to chemotherapy such as Tamoxifen, anti-HER2 antibody, trastuzumab and not as a primary treatment [8]. However, given the low morbidity and mortality of surgery, metastasectomy may be considered as 5-year survival approaches 50% in selected cases [9]. In any case, and especially with solitary lesions, thought should always be given to the possibility of other diseases such as primary lung cancer or a benign disease.
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Surgical technique
