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Eur J Cardiothorac Surg 2005;27:680-685
© 2005 Elsevier Science NL
a Department of Thoracic Surgery, Faculty of Medicine, Université de la Méditerranée (Aix-Marseille II), Sainte-Marguerite Hospital, Assistance Publique-Hôpitaux de Marseille, Marseille Cedex, France
b Department of Thoracic Oncology, Sainte-Marguerite Hospital, Assistance Publique-Hôpitaux de Marseille, Marseille Cedex, France
c Department of Pathology, Sainte-Marguerite Hospital, Assistance Publique-Hôpitaux de Marseille, Marseille Cedex, France
d Department of Medical Information and Biostatistics, Sainte-Marguerite Hospital, Assistance Publique-Hôpitaux de Marseille, Marseille Cedex, France
e UPRES EA 2201, IFR Jean Roche, Marseille Cedex, France
Received 25 August 2004; received in revised form 30 November 2004; accepted 17 December 2004.
* Corresponding author. Address: Sainte-Marguerite Hospital, 270, Bd de Sainte-Marguerite, 13274 Marseille Cedex 09, France. Tel.: +33 491 74 47 41; fax: +33 491 74 45 90. (E-mail: christophe.doddoli{at}mail.ap-hm.fr).
| Abstract |
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Key Words: Non-small-cell lung cancer Mediastinal lymph nodal sampling Lymphadenectomy Prognosis Multivariate analysis
| 1. Introduction |
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Recently, major publications dealing with this topic were reported, based on prospective or large retrospective analysis [17]. However, the debate remains still open, and it appeared to us important to add our experience by conducting a retrospective analysis of a group of 465 consecutive patients who underwent resection of stage I NSCLC during the last 12-year period in one single institution. We investigated on the impact of the extent of the lymph node evaluation at surgery, lymph node sampling (LS) vs. lymphadenectomy (LA), on 30-day mortality and overall survival.
| 2. Materials and methods |
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There were 465 patients, 398 males and 67 females, whose age ranged from 31 to 85 years (mean: 62±10 years). Local-regional lung cancer staging was made with chest X-ray, computed tomography (CT) scan and fiberoptic bronchoscopy. Abdominal ultrasound and CT scan of adrenal glands was obtained routinely, whereas brain CT scan and nuclear bone scan were performed selectively in patients presenting with symptoms. Functional evaluation included spirometry, blood gas analysis at rest, and carbon monoxide diffusion capacity as a routine. Split perfusion nuclear scan was done in patients with an impaired pulmonary reserve (estimated post-resection FEV1 of less than 1l). All patients were operated on by or on the supervision of the same four staff surgeons.
2.2. Operative technique of lymph node evaluation
The technique of the lymph node evaluation was performed at surgeon discretion. The terms used by the surgeon in the operative report to qualify the technique of lymph node evaluation were not taken into consideration. The median number of lymph node sampled was 10 and the median number of ipsilateral mediastinal lymph node stations sampled, as described in the AJCC cancer staging manual [9], was two. Levels 10 and higher were considered N1 lymph nodes. Thus, we chose to define a procedure that harvested 10 or more lymph nodes and sampled two or more ipsilateral mediastinal stations as a lymphadenectomy, by contrast with sampling when one or both criteria were not satisfied. The choice of this cut off for these two variables (number of lymph node and number of mediastinal lymph node stations sampled) was reinforced by the results of ROC curves for the state of death (median of lymph node number=10, sensibility 63%, specificity 48.2% and median of mediastinal lymph node stations number=2, sensibility 66.5%, specificity 43.2%).
Patients were assigned to each study group by an independent observer after reviewing of the operative and pathology reports, and according to the following quantitative criteria. These two techniques were studied for comparison: lymph node sampling (LS; n=207) vs. lymphadenectomy (LA; n=258).
2.3. Statistical analysis
Continuous variables were expressed by means and standards deviations, whereas categorical data were presented using frequencies and percentage. Unpaired t-test were performed when appropriate to compare mean scores across subgroups whereas chi-square or Fisher exact test were used to compare frequencies. Operative mortality included all deaths occurring within 30 days after pulmonary resection or during the same hospital stay.
Survival data were updated for December 2003, by contact with the patient or his referring physician. For patients lost to medical follow-up, missing data were obtained by consulting the City Hall registry.
The following variables were considered as potential prognostic factors of survival: age, gender, surgical procedure (pneumonectomy vs. lesser resections), tumour size (cm), pathology (adenocarcinoma, squamous cell carcinoma vs. others), visceral pleura invasion (absent vs. present), lymphatic or/and blood vessel invasion (absent vs. present), technique of lymph node sampling (LS vs. LA). Survival was estimated using the product limit method of KaplanMeier from the date of the operation and included the operative mortality as well as any cancer-related and unrelated death. Comparisons were made using the log-rank test. P-values of 0.05 or less were considered statistically significant. Univariate and multivariate analysis were performed using Cox proportional hazards regression model to determine factors potentially predicting postoperative survival. The Cox model was used to incorporate in the same model any explanatory variables with a P-value less than 0.20. This statistical analysis was performed by using the SPSS V10.0 software package (SPSS Inc., Chicago, IL).
| 3. Results |
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3.2. Postoperative morbidity and mortality
Fifty major complications (10.8%) occurred (Table 2) and resulted in 13 postoperative fatalities (2.8%). The postoperative mortality rates were 2.4 and 3.1% for LS (n=5) and LA (n=8), respectively (P=0.66). Causes of death were all related to adult respiratory distress syndrome (ARDS).
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Estimated overall survival rate was 61.9% [56.367.5] at 5 years. The survival rates of stage I lung cancer patients with reference to various discrete categorical variables are shown in Table 3. Univariate analysis identified five of them as significant for a poor prognosis: older age, male gender, pathology, bigger tumour size and blood or/and lymphatic vessels invasion. LA was disclosed as a favourable prognosticator at multivariate analysis (Hazard Risk: 1.43; 95% Confidence Interval: 1.002.04; P=0.048, Fig. 1), together with younger patient age, absence of blood and lymphatic vessels invasion, and smaller tumour size (Table 4).
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| 4. Discussion |
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Controversies still exists as to the need for lymphadenectomy vs. lymph node sampling for the cure of early stage NSCLC. The optimal lymph node dissection during lung cancer surgery remains controversial among thoracic surgeons, even in the same team. Proponents of lymphadenectomy point out that the procedure improves the accuracy of disease staging and improves overall results by allowing a complete R0 resection and thereby decreasing local-regional recurrence, and directing more accurate adjuvant therapy. Opponents feel that lymphadenectomy is futile when facing a potentially systemic disease, and postulate higher morbidity and mortality.
The first issue to be addressed is the absence of standardized surgical methods for both sampling and lymphadenectomy, thus hampering any attempt of a comprehensive analysis of internationally available data. Surgeon's inability to intraoperatively determine the presence or absence of tumour within the mediastinal lymph nodes without biopsy was demonstrated by Gaer and Goldstraw [10], who compared the intraoperative visual and tactile evaluation of resected mediastinal lymph nodes with the ultimate histologic diagnosis. Thus, it may be reasonably presumed that the nodal status evaluation through an unopened mediastinal pleura would produce even less accurate results. These data explain why the technique of systematic node sampling should be preferred to random sampling. Systematic node sampling consists of lymph node biopsy at multiple predetermined levels within the mediastinum and bronchopulmonary areas. Complete lymphadenectomy is a concept even less well defined. Indeed, detailed data on the number of removed lymph nodes, as well as the description of nodal stations sampled are seldom reported in the surgical literature, thus precluding any comparison between series. It has been recently suggested that the quality of lymphadenectomy may be reflected quantitatively by the number of totally removed lymph nodes during thoracotomy and pathologically evaluated [6,7,11]. However, reported cut-off values vary greatly from 6 to 15. From a pragmatic point of view, the number of lymph nodes may be increased artificially when pieces of lymph nodes had been fragmented during dissection. Furthermore, as demonstrated by Riquet et al., there are wide variations of the number of lymph nodes at a given station between individuals [12]. All these considerations led us to define in a mixed way a procedure that harvested 10 or more lymph nodes and sampled two or more mediastinal stations as a lymphadenectomy, by contrast with sampling when one or both criteria were not satisfied. Of note, these definitions were in accordance with those used by the Eastern Cooperative Oncology Group in the ECOG 3590 trial (Intergroup, INT 0115) [3].
While it is commonly accepted that for an appropriate staging a minimum of hilar and mediastinal lymph nodes has to be removed and examined [2,3], the therapeutic efficacy of mediastinal lymphadenectomy is still under debate. The first randomised studies published in the English-written literature included a few number of patients, and failed to demonstrate any significant difference of outcome in patients having received radical systematic lymphadenectomy (LA) when compared to those having undergone lymph node sampling (LS) [1,2]. However, analysis of subgroups of patients according to the nodal status suggested that LA had a tendency to prolong relapse-free survival significantly with a borderline effect on overall survival in patients with minimal N disease (pN1 disease or pN2 disease with involvement of only one lymph node level) [2]. A Chinese group demonstrated recently on the basis of a large randomised clinical trial a significant survival advantage with LA over LS, and the subgroup analysis disclosed a significant benefit in stages I and IIIA NSCLC patients, and a marginally significance in stage II patients [5].
Whether or not removing healthy lymph nodes improves survival in lung cancer is still a moot point. Considering our data and these recent publications [57], it may be suggested that there is a place for mediastinal lymphadenectomy for pathological stage I disease to improve survival, even if the adequate definition of mediastinal lymphadenetomy will still remain an open issue. Obviously, the value of mediastinal lymphadenectomy in early stage NSCLC needs to be confirmed by at least another phase III study, now in progress (American College of Surgeons Oncology Group, ACOSOG protocol Z0030). Even if stage migration, the so-called Will Rogers phenomenon, interferes clearly with these findings between LA and LS, a therapeutic efficiency of lymphadenectomy may be hypothesized. This therapeutic efficiency of LA may be grounded through the presence of occult micrometastatic disease in the lymph nodes. The concept of occult micrometastatic disease originates from the detection of metastatic cells which are not detected by current clinical staging examinations and conventional histopathologic methods, using immunohistochemical or molecular methods. The presence of micrometastatic cells in the lymph nodes, the bone marrow, and the peripheral blood, can be considered as a marker for primary tumors with a high metastatic potential [1315]. Osaki et al. demonstrated recently that micrometastasis in the bone marrow and the lymph nodes of patients with completely resected stage I NSCLC were detected with the same frequency (27.8%), without evidence of any relationship between these two sites, suggesting different regulations or mechanisms [13]. LA allows to remove micrometastatic lymph nodes and, in turn, increases the proportion of complete R0 resections, leaving no residual disease. A German group investigated on the therapeutic effectiveness of LA vs. LS in N0 patients as determined by conventional histopathological analysis, but with nodal micrometastases as detected by using immunohistochemical methods. Unfortunately, they failed to demonstrate any influence on prognosis of the type of lymphadenectomy in such patients with early disseminated tumour cells in lymph nodes [4]. Paradoxically, a survival benefit of LA was suggested in patients with a N0 disease as defined with both routine histology and immunohistochemistry.
The operative mortality observed in this series was in line with current standards [16]. The risk from pulmonary resection is dependent on the extent of resection. In that way, it is important to point out that the proportion of patients having undergone a pneumonectomy was about 13% in the present series, a rate that is in accordance with what is usually reported in this early stage, ranging from 5 to 20% [6,7,1720]. Of concern is the fact that the technique of lymph node sampling did not influence postoperative mortality or major morbidity accordingly to previous claims [5,7], but in contrast with others [1]. Potential complications of lymphadenectomy may arise from injuries to the bronchial arteries and nerves, the tracheobronchial tree itself, and recurrent nerves. Mediastinal lymphadenectomy also impairs the lymphatic backflow and may add to pulmonary oedema. The occurrence of respiratory complications, i.e. pneumonia and ARDS, was very similar in the two groups. The incidence of laryngeal nerve paralysis was higher in the LA group although the difference did not reach statistical significance. An impaired laryngeal mobility can be dramatic after lung resection, and it should be tracked and treated as soon as possible. Its consequences include swallowing disorder and ineffective cough, both concurring to life-threatening events [21]. Our policy included immediate laryngeal examination and delayed oral feeding, and sometimes early thyroplasty as advocated by some authors [22]. This approach maintained related respiratory events at a relatively low level.
To conclude, importance of lymphadenectomy affects patients outcome, while it does not enhance the operative mortality. A minimum of 10 lymph nodes assessed, and two mediastinal stations sampled are suggested as possible pragmatic markers of the quality of lymphadenectomy.
| Footnotes |
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Presented at the joint 18th Annual Meeting of the European Association for Cardio-thoracic Surgery and the 12th Annual Meeting of the European Society of Thoracic Surgeons, Leipzig, Germany, September 1215, 2004. | References |
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