Diagnostic yield of pleural thoracentesis in case of suspected malignant pleural effusion (MPE) varies according to the histological type of the primary tumor (1,2), to the local extent of the disease (involvement of both visceral and parietal pleura) (3) and of course to the expertise (4). In patients with non-small cell lung cancer (NSCLC) and MPE, the evidence of malignant cells in the pleura is critical as their presence directly means that the patient presents with metastatic disease, and therefore he will be treated accordingly despite the fact that there is no evidence of other metastatic sites (5). In the case of absence of malignant cells in fluid cytology the best way to confirm or rule out diagnosis is to “go and look inside”, by thoracoscopy, a minimally invasive and safe technique, performed either by a pulmonologist or a thoracic surgeon (6). Furthermore, in the era of personalization of the therapeutic options, the need for large tissue samples provides important information on molecular factors that are actually in use to treat those patients, but also new factors may be discovered in the near future and used if stocking tissue samples (bio-banking) (4). Considering this, thoracoscopy is the examination of choice for all patients with lung cancer and MPE.
However, all centers do not dispose thoracoscopy as an option in their settings as this procedure requires expertise (7). Therefore, the idea behind our study (8) was what do if no thoracoscopy, although in our center we dispose this technique. More specifically, we would like to know whether the combination of all non-invasive tests, including chest computed tomography (CCT), positron emission tomography (PET), together with pleural cytology, help in diagnosing patients with MPE from lung cancer (8). Indeed, our study has limitations as it is a retrospective one. For instance, about half of the patients benefited of PET and the mismatch between fluid cytology, CCT and PET, may lead to a likely underpowered statistical analysis (8). Yet, at the metastatic stage of the disease PET is not systematically recommended (5).
Some important points in our study are that our population was homogenous (only lung cancer patients with MPE), coming from a single center (9). These two facts prevent from suffering of significant inclusion biases either from studying an heterogenous population (many different primary carcinomas) and/or many different centers with variations in the yield of the different examinations tested, such as pleural cytology, CCT and PET. In our study (8), taking the yield of pleural fluid cytology separately and compared to the current bibliography, our yield was of the higher in this patient population, and it was enhanced after thoracoscopy, a method that systematically may not be used, yet even in case of surgically treated peripheral NSCLC, positive pleural lavage may totally change the treatment strategy as it is a factor of poor survival (10,11). We agree that the results of CCT may be lower than the reported in the literature regarding MPE in general (9), and despite the fact of lung cancer patients, we believe that an important issue is the systematically use of thin sections to better look inside the pleura, and even though it is hard to detect specific features because of the partial volume effect and the growth of pleural nodules within fibrous tissues and exudates (12). PET in NSCLC (5) indeed has to be used only in case of possible radical surgery to detect distant metastasis, and our study (8) confirms the poor utility of PET in this patient population (7), and of course this is also true in patients with malignant pleural mesothelioma (13). When we tried to correlate these non-invasive techniques, no relation was found (8). Yet, their combination increased the yield up to 90%, and this is a novel information, although in our study we had a high proportion of adenocarcinomas (7).
But the most important message of our study, is that we may improve the diagnostic yield by the combination of all these non-invasive techniques, still a good number of patients, if not all, will necessitate thoracoscopic biopsy for diagnostic purposes, but also for “molecular staging”.
Conflicts of Interest: The authors have no conflicts of interest to declare.
- Arnold DT, De Fonseka D, Perry S, et al. Investigating unilateral pleural effusions: the role of cytology. Eur Respir J 2018;52. [Crossref] [PubMed]
- Anevlavis S, Kouliatsis G, Sotiriou I, Koukourakis MI, Archontogeorgis K, Karpathiou G, et al. Prognostic factors in patients presenting with pleural effusion revealing malignancy. Respiration 2014;87:311-6. [Crossref] [PubMed]
- Froudarakis ME, Plojoux J, Kaspi E, et al. Positive pleural cytology is an indicator for visceral pleural invasion in metastatic pleural effusions. Clin Respir J 2018;12:1011-6. [Crossref] [PubMed]
- Bibby AC, Dorn P, Psallidas I, et al. ERS/EACTS statement on the management of malignant pleural effusions. Eur Respir J 2018;52. [Crossref] [PubMed]
- Postmus PE, Kerr KM, Oudkerk M, et al. Early and locally advanced non-small-cell lung cancer (NSCLC): ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 2017;28:iv1-iv21. [Crossref] [PubMed]
- Rodriguez-Panadero F. Medical thoracoscopy. Respiration 2008;76:363-72. [Crossref] [PubMed]
- Lim JH, Ryu JS. Current perspective on the diagnosis of malignant pleural effusion. J Thorac Dis 2019;11:S1234-6. [Crossref]
- Brun C, Gay P, Cottier M, et al. Comparison of cytology, chest computed and positron emission tomography findings in malignant pleural effusion from lung cancer. J Thorac Dis 2018;10:6903-11. [Crossref] [PubMed]
- Arnold DT, Maskell NA. Imaging for malignant pleural effusions- still no routine role of PET. J Thorac Dis 2019;11:1079-81. [Crossref]
- Goldstraw P, Lim E. Value of intraoperative pleural lavage in staging non-small cell lung cancer. J Thorac Cardiovasc Surg 2004;128:331. [Crossref] [PubMed]
- Lim E, Clough R, Goldstraw P, et al. Impact of positive pleural lavage cytology on survival in patients having lung resection for non-small-cell lung cancer: An international individual patient data meta-analysis. J Thorac Cardiovasc Surg 2010;139:1441-6. [Crossref] [PubMed]
- Jiang T, Zheng X, Liu S. Thin-section CT as an optimal diagnostic tool in the evaluation of dry pleural dissemination in non-small cell lung cancer. Radiology 2012;262:368-9; author reply 9. [Crossref] [PubMed]
- Woolhouse I, Bishop L, Darlison L, et al. British Thoracic Society Guideline for the investigation and management of malignant pleural mesothelioma. Thorax 2018;73:i1-30. [Crossref] [PubMed]