Comparative studies of computerized tomography and mediastinoscopy for the staging of bronchogenic carcinoma

Computed Tomography and Mediastinoscopy in the Assessment of Resectability of Lung Cancer

In order to assess the potential of computed tomography (CT) of the mediastinum and mediastinoscopy in the staging of lung cancer, 125 patients were examined. Of these, 104 underwent thoracotomy, at which there was no evidence of mediastinal tumour involvement in 79 while 25 patients had signs of tumour spread. The sensitivity and specificity of CT were 87.0 per cent and 95.8 per cent, respectively, in the detection of direct tumour extension with a mediastinal mass. When lymph node enlargement was the sole finding, CT did not provide any differentiation between benign and malignant lymphadenopathy. The mediastinal involvement was inaccessible on mediastinoscopy in 18 cases (72%). Despite the surperior sensitivity of CT it was often difficult to determine whether direct tumour infiltratin of mediastinal structures had occurred. It was concluded that CT is necessary for screening the entire mediastinum and, when it reveals no evidence of mediastinal tumour spread, mediastinoscopy will yield no further information. Mediastinoscopy will help to correctly identify accessible mediastinal lymph node involvement of the superior mediastinum and to define the mediastinal tumour invasion in doubtful cases.

Correlative anatomy for thoracic inlet; glottis and subglottis; trachea, carina, and main bronchi; lobes, fissures, and segments; hilum and pulmonary vascular system; bronchial arteries and lymphatics

Because it is relatively inexpensive and universally available, standard radiographs of the thorax should still be viewed as the primary screening technique to look at the anatomy of intrathoracic structures and to investigate airway or pulmonary disorders. Modern trained thoracic surgeons must be able to correlate surgical anatomy with what is seen on more advanced imaging techniques, however, such as CT or MRI. More importantly, they must be able to recognize the indications, capabilities, limitations, and pitfalls of these imaging methods.

Clinical prognostic factors in surgically treated stage IIIA-N2 non-small cell lung cancer: analysis of the literature

There remains controversy on the prognostic value of several common clinical factors in NSCLC patients with resected N2-disease. The aim of this paper is to give a comprehensive overview of the available data on this issue. Literature data on surgically treated N2-NSCLC-patients from 1980-1995, peer reviewed and listed in Index Medicus, were analysed. Reported and calculated or estimated survival data were indexed. Eighteen series were selected: in 12 of them, direct comparisons between survival curves of subgroups are reported; six contained sufficient data to make comparisons of survivors at 5 years; three of them also made a multivariate Cox model. The analysis of prognostic factors in a single study was often hampered by the limited number of patients. Nonetheless, it could be concluded that patients with a clinical N0- or N1-status (so-called unforeseen N2) do better. There was no clear difference between patients undergoing lobectomy or pneumonectomy. There was strong evidence that N2-patients with a less advanced primary tumour (T-stage) have a better prognosis, and this is the case for all operable T-stages (T1 versus T2, T1 versus T3, T2 versus T3). Squamous cell type was a favourable prognostic factor, as was the presence of only one metastatic mediastinal lymph node station or absence of metastases to the subcarinal nodes. There was some evidence that the presence of extracapsular spread in metastatic MLN is an unfavourable finding. Stratification for these prognostic factors could help in the planning of future trials on combined modality treatment in N2-NSCLC.

Computerised tomography does not predict N2 disease in patients with lung cancer

BACKGROUND

Mediastinal node involvement in primary lung cancer determines the staging and prognosis of the patient, and as these nodes can be seen on the computerised tomography (CT) scan of the chest it is a temptation to diagnose malignant involvement if the nodes appear enlarged. However, initial experience with mediastinal node mapping at lung resection demonstrated this extrapolation to be unreliable and misinterpretation of enlarged nodes on CT may lead to misdiagnosis and prejudice the patient's management.

AIM

To demonstrate that the sensitivity, specificity, and accuracy of the CT to detect malignant mediastinal nodes is too low to use size of node on CT as representative of malignant involvement.

METHODS

One hundred and fifty-three sequential patients with resectable lung cancer were studied with preoperative CT. Two radiologists determined the preoperative T and N status from these studies with nodes of 1.5 cm or larger diagnosed abnormal. These results were compared to the results of subsequent node mapping performed after lung resection.

RESULTS

Sensitivity was found to be 26%, specificity to be 81% and overall accuracy 69%--too low to justify the diagnosis of N2 disease on size of 1.5 cm or larger. CT is not a valid means of diagnosing malignant involvement of mediastinal nodes.

Prognostic significance of computed tomography in resected N2 lung cancer

We reviewed 124 patients from 1982 to 1988 who had a resected primary non-small cell lung cancer metastatic to mediastinal (N2) lymph nodes and a preoperative assessment of the mediastinum with computed tomography of the chest. Sixty-three patients studied had computed tomographic evidence of mediastinal lymph node enlargement. In these patients the survival at 5 years was only 6.6%, compared with the 5-year survival of 13.5% in 61 patients in whom the mediastinum was normal. Plain chest roentgenography with evidence of mediastinal adenopathy did not predict a poorer outcome. In addition, patients with tumors located in the left upper lobe were found to have an improved survival. These patients had a 5-year survival of 20.8%. Tumor histology, central location of the tumor, extranodal extension, and type of resection did not result in a significant survival difference.

Computed tomography to stage lung cancer. Approaching a controversy using meta-analysis

The ability of computed tomography (CT) to detect mediastinal lymph node metastases from nonsmall cell bronchogenic lung cancer is highly controversial, as evidenced by reported accuracies ranging from 0.35 to 0.95 over the past eight years. We examined all studies on this matter published between January 1980 and April 1988, both to describe the overall experience and to identify characteristics (study design and methodology and CT scan techniques) that influenced reported accuracy. Of 79 relevant publications, 37 were excluded because they were review reports, assessed small cell lung cancer, or contained insufficient evidence to construct a contingency table (CT result versus node histology). The pooled, unweighted (weighted) results based on the remaining 42 studies were as follows: sensitivity, 0.79 (0.83); specificity, 0.78 (0.81); accuracy, 0.79 (0.81). Using a node size greater than 1.0 cm to define a "positive" CT result, as compared to a smaller diameter, was associated with significantly higher specificity, 0.89 versus 0.76, and accuracy, 0.86 versus 0.75 (p less than or equal to 0.005), but not sensitivity, 0.79 versus 0.75. The observed differences in accuracy between a fourth generation CT (0.83) and either a third or a second generation CT, (0.77 and 0.78, respectively) were not significant at p less than 0.05. No characteristics, either singly or in combination, resulted in accuracies exceeding 0.86. There exists random variation of individual study results around an overall mean accuracy of only 0.79, which is marginally improved by advances in CT technology and methods. Significant advances in the noninvasive detection of lymph node metastases must await an approach fundamentally different from CT-determined node size.

Computed tomography in bronchogenic carcinoma

As was indicated at the beginning of this review, a concensus does not exist regarding many aspects of the use of CT in evaluating bronchogenic carcinoma. When and how CT is used, therefore, becomes a function of the beliefs of the physician caring for the patient. The radiologist must be familiar with this philosophy to be able to advise when CT will be of value. Despite all of the variables considered on the preceding pages, there are some facts. (1) Normal mediastinal lymph nodes may be larger than 1 cm in maximal transverse diameter; the majority are not. (2) An enlarged node (independent of definition) need not harbor metastases. Histologic proof is necessary, especially if this information will preclude surgery. (3) CT less frequently offers usable information in small peripheral cancers. The use of CT in peripheral cancers is very much dependent on the surgeon's philosophy. (4) Important information for patient care is more frequently obtained in patients with central lesions or peripheral lesions associated with abnormal hili or mediastinums. This is also closely related to surgical philosophy. (5) Prediction of either chest wall or mediastinal invasion is treacherous and should only be diagnosed when the findings are certain.

Complications of mediastinoscopy

From 1968 to 1987, mediastinoscopy was performed on 2021 consecutive patients. The procedure was carried out in 35.7 per cent on patients with a pulmonary infiltrate and in 28.8 per cent with bronchogenic carcinoma. Mediastinoscopy was positive in 54 per cent of the cases. The total number of complications was 2.3 per cent (47/2021). There were four cases with major haemorrhage, three tracheal ruptures and three wound infections. Recurrent nerve paralysis was verified in three patients and pericardial rupture in two patients. The total of major complications was 0.5 per cent (10/2021). There was no deaths in this series. In the authors' opinion, mediastinoscopy can be regarded as an effective and safe procedure in the hands of an experienced surgeon.