Liquid Biopsies from Pleural Effusions and Plasma from Patients with Malignant Pleural Mesothelioma: A Feasibility Study

Our plain-English summary of Liquid Biopsies from Pleural Effusions and Plasma from Patients with Malignant Pleural Mesothelioma: A Feasibility Study, by G. Moretti, P. Aretini, F. Lessi, et al (Cancers, 2021).

The study

• Authors: G. Moretti, P. Aretini, F. Lessi, C.M. Mazzanti, G. Ak, M. Metintaş, C. Lando, R.A. Filiberti, M. Lucchi, A. Bonotti, R. Foddis, A. Cristaudo, A. Bottari, A. Apollo, M. Del Re, R. Danesi, L. Mutti, F. Gemignani, S. Landi
• Journal: Cancers
• Published: 2021;13(10)
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is a fatal tumor with a poor prognosis. The recent developments of liquid biopsies could provide novel diagnostic and prognostic tools in oncology. However, there is limited information about the feasibility of this technique for MPMs. Here, we investigate whether cancer-specific DNA sequences can be detected in pleural fluids and plasma of MPM patients as free circulating tumor DNA (ctDNA).

Methods: We performed whole-exome sequencing on 14 tumor biopsies from 14 patients, and we analyzed 20 patient-specific somatic mutations with digital droplet PCR (ddPCR) in pleural fluids and plasma, using them as cancer-specific tumor biomarkers.

Results: Most of the selected mutations could be detected in pleural fluids (94%) and, noteworthy, in plasma (83%) with the use of ddPCR. Pleural fluids showed similar levels of somatically mutated ctDNA (median = 12.75%, average = 16.3%, standard deviation = 12.3) as those detected in solid biopsies (median = 21.95%; average = 22.21%; standard deviation = 9.57), and their paired difference was weakly statistically significant (p = 0.048). On the other hand, the paired difference between solid biopsies and ctDNA from plasma (median = 0.29%, average = 0.89%, standard deviation = 1.40) was highly statistically significant (p = 2.5 × 10-7), corresponding to the important drop of circulating somatically mutated DNA in the bloodstream. However, despite the tiny amount of ctDNA in plasma, varying from 5.57% down to 0.14%, the mutations were detectable at rates similar to those possible for other tumors.

Conclusions: We found robust evidence that mutated DNA is spilled from MPMs, mostly into pleural fluids, proving the concept that liquid biopsies are feasible for MPM patients.

In plain English

This feasibility study tested whether tumor-specific DNA mutations could be found in pleural fluid and plasma of people with malignant pleural mesothelioma (MPM). It used samples from 14 patients diagnosed with MPM at three hospital centers in Genoa and Pisa, Italy, and Eskisehir, Turkey. The authors sequenced each tumor, selected a few mutations per patient, and measured tumor-confirmed mutations in pleural fluid and plasma when available. After two probably inherited mutations were set aside, 16 of 17 analyzable mutations were detected in pleural fluid and 15 of 18 in plasma. Mutated DNA made up a median of 21.95% in tumor samples, 12.75% in pleural fluid and 0.29% in plasma. The difference between tumor and pleural fluid was statistically significant by one test (p = 0.0237) but not by another (p = 0.0648). The difference between tumor and plasma was significant by both tests. The article does not report any analysis of asbestos exposure. The authors concluded that liquid biopsies are feasible in MPM. They noted that clinical information was limited and that it is unknown whether detection works at earlier disease stages.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory feasibility study of stored tumor, pleural fluid and plasma samples (tumor sequencing followed by digital droplet PCR)
• Who was studied: Samples from 14 patients diagnosed with malignant pleural mesothelioma at three hospital centers: 7 from San Martino Hospital, Genoa, Italy (diagnosed 2002–2012), and 7 from Pisa, Italy (2 patients) and Eskisehir Osmangazi University Hospital, Turkey (5 patients) (2017–2019)
• Exposure: The article does not report an analysis of asbestos exposure. The study measured tumor-specific DNA mutations in tumor, pleural fluid and plasma.
• Main results:
  • Of 39 mutations selected, 22 were confirmed in solid tumor biopsies and went on to testing in pleural fluid and plasma
  • 16 of 17 analyzable mutations were detected in pleural fluid
  • 15 of 18 analyzable mutations were detected in plasma, at levels from 0.14% to 5.57%
  • In the Genoa group, 6 of 7 patients showed tumor DNA in their plasma
  • Share of mutated DNA in solid tumor samples versus pleural fluid: median 21.95 vs 12.75; average 22.21 (standard deviation 9.57) vs 16.3 (standard deviation 12.3)
  • The tumor versus pleural fluid difference was statistically significant with the paired Student's t-test (p = 0.0237)
  • The tumor versus pleural fluid difference was not statistically significant with the Wilcoxon test (p = 0.0648)
  • Mutated DNA in plasma was much lower than in tumor (median 0.29, average 0.89, standard deviation 1.40). The difference was statistically significant by both tests (p = 2.49 times 10 to the minus 7, and p = 3.2 times 10 to the minus 4).
  • Mutation percentages in pleural fluid differed from those in tumor biopsies by about 7.5% on average
  • In two Genoa patients, two mutations were likely inherited (germline) rather than tumor-specific
  • No statistically significant correlation was found between the amount of mutated DNA and overall survival
• The authors' conclusion: The authors concluded that liquid biopsies are feasible in MPM and could lead to new tools for managing these patients
• Limitations the authors state:
  • Clinical information from the Genoa and Pisa biobanks was limited
  • It is not known whether mutated DNA can be detected in patients with earlier-stage disease
  • Only a few milliliters of plasma were available, which limited how much DNA could be analyzed
  • The survival analysis may have had low statistical power
  • Blood cells (buffy coat) were not available for the Genoa patients, so their tumor and blood DNA could not be sequenced side by side

Topics

Medical terms in this study, explained in our Lexicon: Pleural Effusion, Pleural Mesothelioma, Prognosis, ctDNA, Somatic Mutation, Biomarker.

Related studies

• Comparative analysis of genetic variants in pleural fluids and solid tissue biopsies of pleural mesothelioma patients: Implications for molecular heterogeneity assessment — R. Silvestri, F. Rea, et al. (2024)
• Circulating long non-coding RNA GAS5 (growth arrest-specific transcript 5) as a complement marker for the detection of malignant mesothelioma using liquid biopsies — D.G. Weber, S. Casjens, et al. (2020)
• miR-625-3p and lncRNA GAS5 in Liquid Biopsies for Predicting the Outcome of Malignant Pleural Mesothelioma Patients Treated with Neo-Adjuvant Chemotherapy and Surgery — J. Kresoja-Rakic, A. Szpechcinski, et al. (2019)
• Tasks and Experiences of the Prospective, Longitudinal, Multicenter MoMar (Molecular Markers) Study for the Early Detection of Mesothelioma in Individuals Formerly Exposed to Asbestos Using Liquid Biopsies — D.G. Weber, S. Casjens, et al. (2023)
• Comparison between plasma and serum osteopontin levels: usefulness in diagnosis of epithelial malignant pleural mesothelioma — A. Cristaudo, R. Foddis, et al. (2010)
• Determination of 5,10,15,20-tetra-(m-hydroxyphenyl)chlorin in human plasma by high performance liquid chromatography — Q. Wang, H.B. Ris, et al. (1993)

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