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Occupational asbestos exposure has been endemic in Portsmouth. A retrospective case note analysis of 50 patients who underwent thoracoscopy over a 2-year period from January 2003 was undertaken. Biopsies were taken in 47 cases, 31 of which showed malignant mesothelioma. Thirty seven percent of those without a history of direct exposure to asbestos had mesothelioma, implying that even in the absence of an exposure history a low threshold for investigation should be adopted for the local population. There was no mortality or significant morbidity associated with the procedure. Medical thoracoscopy is safe and effective in the diagnosis of benign and malignant pleural disease particularly in this high risk population.
Thoracoscopy was introduced by Jacobaeus in 1910 to investigate the cause of exudative pleural effusions, particularly those secondary to TB. There remains debate as to whether this procedure is in the domain of the physician or the surgeon.
Surgical thoracoscopy requires general anaesthesia with selective endobronchial intubation and typically three points of entry through the chest wall. Medical thoracoscopy requires local anaesthesia with premedication and usually one or two points of entry.
Medical thoracoscopy has both a diagnostic and a therapeutic role.
Faced with an undiagnosed pleural effusion and a high index of suspicion of mesothelioma, recurrent pleural aspiration is best avoided as it carries risk of needle track spread of the disease. Thoracoscopy not only allows the removal of the pleural fluid and biopsies under direct vision, but also pleurodesis at the same time.
The Queen Alexandra Hospital in Portsmouth is a busy District General hospital. Due to the close proximity of the Portsmouth Dockyards, the local population has a high prevalence of asbestos-related respiratory disease including malignant mesothelioma.
In selected patients where no contraindications are observed, medical thoracoscopy seems to be a safe uncomplicated technique with high diagnostic accuracy in the hands of the physician.
The aim of this study was to assess the validity of this statement in this unit serving the local population where asbestos exposure has been endemic.
Materials and methods
Fifty patients who had undergone medical thoracoscopy between 1 January 2003 and 31 December 2005, whatever the indication, were selected at random. Only 50 were selected due to the constraints of the study. A total of 79 thoracoscopies took place in this period, performed/supervised by three different operators. None of the patients underwent the procedure more than once.
In every case the smoking history, exposure to asbestos, occupation, relevant past medical history—including personal history of cancer, was reviewed directly from the case notes. Those who were ‘never smokers’ were deemed to have no smoking history. Asbestos exposure was defined as documentation of recollection by the patient of direct exposure ± an occupation of high risk (e.g. pipe lagging, working in the Dockyards, Naval stokers).
Thoracocentesis was performed in all cases, the results were noted which included the biochemistry of the pleural fluid, results from microscopy, culture and sensitivity and cytology. These results were obtained via ‘apex’ the hospital computer system that stores all laboratory investigation results. Histology results were gained by the same means.
Thoracoscopy was performed as described in ‘Thoracoscopy for physicians’
under local anaesthesia. Following removal of the fluid a rigid thoracoscope was inserted and the pleural cavity inspected. Biopsies were taken under direct visualisation in all suspect areas of the parietal pleura, but never of the visceral pleura. Where indicated, talc poudrage was applied in the pleural space. An intercostal chest drain was inserted before wound closure to allow for evacuation of fluid and air.
The ECG, blood pressure and oximetry were monitored throughout the procedure and continued for the next 6h post-procedure.
The chest drain was not clamped and high volume low pressure suction was applied. In the absence of excessive fluid drainage (>200ml/day), the drain was removed 72h after insertion.
Complications were recorded by a review of the individual case notes.
The characteristics of the patients are shown in Table 1. The mean age of the study population at the time of the procedure was 72 (range 49–84).
All patients underwent thoracocentesis prior to thoracoscopy. In 48 cases pleural fluid samples were sent for biochemical analysis, all were an exudate (mean protein 49 and mean LDH 1401). In the two cases where this test was not performed the final diagnosis was mesothelioma. In all 50 cases pleural fluid was sent for microscopy, culture and sensitivities, all were sterile. The cytology results are detailed in Table 2.
Table 2Initial diagnoses based on thoracocentesis and cytology.
No biopsies were taken in three cases, firstly in a 49-year-old woman with known metastatic carcinoma of the breast, visualisation of the pleural space was not possible and the procedure abandoned. In the second case, no abnormality of the pleura was noted and clinically the effusion was suspected to be parapneumonic. In the third case, extensive adhesions made continuation of the procedure hazardous, malignant mesothelioma was diagnosed following thoracotomy under general anaesthesia. Image guided cutting needle biopsy could have been considered in this case post to thoracoscopy.
One of the cases suspected of mesothelioma was confirmed when the pleural biopsies and subsequent skin biopsies were compared. Immunostaining was unable to firmly make the diagnosis of mesothelioma in the remaining two cases.
The population undergoing thoracoscopy were selected not to include those with positive cytology from simple aspiration. 3/31 cases of mesothelioma had positive cytology prior to the procedure (Table 4).
Table 4Cytology results in the presence or absence of mesothelioma.
If positive cytology is defined as being highly suggestive of mesothelioma as oppose to atypical or reactive mesothelial cells, a sensitivity of 3/31 and a specificity of 100% from pleural fluid cytology is obtained from this data. In all three cases where the histology was suggestive but not diagnostic of mesothelioma, cytology demonstrated either reactive or inflammatory cells.
For the other malignancies involving the pleura the results from cytology were non-diagnostic which was the indication for thoracoscopy.
The results from the pleural biopsies were compared with the history of asbestos exposure. As expected, where the diagnosis is malignant mesothelioma, there is often a good history of asbestos exposure (Fig. 1).
There were a significant number of cases with no history of asbestos exposure where subsequently either a diagnosis mesothelioma or pleural fibrosis was made (Fig. 2).
The complications of thoracoscopy are shown in Table 5. There were no deaths directly attributable to the procedure, however, one 81-year-old gentleman died 3 days post-thoracoscopy from renal failure associated with his metastatic prostate cancer, confirmed on histology from the procedure. Of the 3 cases of infection around the wound site, none resulted in severe sepsis or empyema, Staphylococcus aureus was implicated in one case and Staphylococcus epidermidis in another. Nine of the 50 patients experienced some form of complication (18%).
There were five cases of failure of lung re-expansion or ‘trapped lung’ all of which occurred in the context of mesothelioma. One patient had a persistent air leak post-thoracoscopy that required VATS. There was no documented trauma to the visceral pleura noted in the thoracoscopy report, but this remains a possibility; the air leak may have resulted from the shearing forces applied to the visceral pleura upon re-expansion.
The role of thoracoscopy in the diagnosis of pleural effusions of unknown aetiology and particularly in the context of mesothelioma is established.
What was strikingly apparent from the above results was the prevalence of pleural malignancy within the population undergoing thoracoscopy. This is at least partially attributable to the prevalence of asbestos exposure within the local population, but also due to the selection of those undergoing the procedure.
All of the patients, prior to thoracoscopy, had pleural fluid sent for microbiological studies, all of which were known to be negative before the procedure was undertaken. It is routine practice in this unit for all cases of suspected thoracic malignancy to have a staging CT of the thorax ± a bronchoscopy prior to discussion at a multi-disciplinary team (MDT) meeting. Any cytology results from a pleural aspirate are also discussed. Only those cases not amenable to bronchoscopy or CT/US-guided biopsy in the context of a pleural effusion and non-diagnostic cytology are put forward for thoracoscopy. Given this selection process, which aims to exclude pleural infections and often provides alternate means for the diagnosis of lung cancer, it is hardly surprising that the large majority cases undergoing medical thoracoscopy result in the diagnosis of mesothelioma. This retrospective study shows a selection bias toward including patients with known malignancy or a high pre-test probability of malignancy, particularly mesothelioma.
In all 29/50 of the patients undergoing thoracoscopy had documented asbestos exposure, so increasing the pre-test probability of pleural malignancy. Mesothelioma occurred in the context of asbestos exposure which is to be expected, however it was the diagnosis in 37% of those without asbestos exposure. This is probably a reflection of the strict criteria for asbestos exposure used in this study, the characteristics of the local population and selection bias outlined above. Even given these areas of bias, in this particular population there should be a low threshold of clinical suspicion of pleural malignancy in the right clinical setting even in the absence of a history of asbestos exposure.
In this study cytological evaluation was found to be of limited use, probably due in part to the selection bias, the majority of the cases had non-dignostic cytology, hence the need to proceed to thoracoscopy, but also as cytology is known to be of limited diagnostic use in the context of mesothelioma.
Closed needle biopsies prior to thoracoscopy are not undertaken routinely in this unit. In a population where the prevalence of mesothelioma and clinical suspicion is relatively high, repeatedly traversing the pleural and thoracic wall could pre-dispose to seeding of tumour. This risk outweighs the potential diagnostic benefit of a closed needle biopsy. In a large retrospective study only 7% of patients with a malignant effusion had a positive closed needle biopsy when the fluid cytology was negative.
In 10% of the patients from this study there was failure of lung expansion following drainage of the pleural effusion and talc pleurodesis; all had malignant mesothelioma. In these cases encasement of the lung by tumour prevented reexpansion. There were no complications directly attributable to pleurodesis. The complication rate for thoracoscopy was low, with no mortality or significant morbidity. Other larger studies have found the mortality rate to be less than 1%.
Who should perform thoracoscopy remains an area of debate. This study has demonstrated that in a select group of patients, diagnostic pleural biopsy with talc pleurodesis is achieved with high diagnostic accuracy and a high degree of safety.
It could be argued given the poor prognosis of those with pleural malignancies; there is little need to pursue the diagnosis until therapeutic options have been developed. Making the diagnosis gives prognostic information to the patient, may have financial implications and in this high risk population making a diagnosis of benign pleural disease is also useful. Having made the diagnosis of mesothelioma a cohort of patients are identified who could be eligible for therapeutic trials. Thoracoscopy via the use of pleurodesis has an established role in symptom management.
In this region of the county where occupational asbestos exposure is endemic, medical thoracoscopy is safe and effective in the diagnosis of benign and malignant pleural disease.
Miller Jr, J.I.
Therapeutic thoracoscopy: new horizons for an established procedure (Editorial).