Clinical Features in Patients With Malignant Pleural Mesothelioma With 5-Year Survival and Evaluation of Original Diagnoses

Our plain-English summary of Clinical Features in Patients With Malignant Pleural Mesothelioma With 5-Year Survival and Evaluation of Original Diagnoses, by J. Paajanen, S. Laaksonen, I. Ilonen, et al (Clinical Lung Cancer, 2020).

The study

• Authors: J. Paajanen, S. Laaksonen, I. Ilonen, T. Vehmas, M.I. Mäyränpää, E. Sutinen, E. Kettunen, J.A. Salo, J. Räsänen, H. Wolff, M. Myllärniemi
• Journal: Clinical Lung Cancer
• Published: 2020;21(6):e633-e639
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Malignant pleural mesothelioma (MPM) is a fatal malignancy strongly associated with previous asbestos exposure. Overall survival remains dismal, partly owing to poor response to available treatment. The aims of this study were to evaluate diagnostic accuracy in a group of patients with MPM with an unusually long survival time and to assess the factors related to this prolonged survival.

Materials And Methods: Forty-three patients with overall survival exceeding 5 years were accepted to the long-term survivor (LTS) group, and these patients were compared with 84 patients with epithelial MPM. Data were collected from various national registries and electronic medical records. In addition, all available histopathologic diagnostic samples and computed tomography studies were re-evaluated by experienced specialists.

Results: Our study showed a good diagnostic accuracy, with only 1 (0.5%) patient having an incorrect MPM diagnosis. Two (0.9%) localized malignant mesotheliomas and 2 (0.9%) well-differentiated papillary mesotheliomas were also found. LTS patients were younger, more frequently female, had a better performance status at time of diagnosis, and had less evidence of prior asbestos exposure. In multivariate analysis, we showed tumor size, Eastern Cooperative Oncology Group performance status, and first-line treatment (both surgery and chemotherapy) to be associated with survival time.

Conclusion: We confirmed the diagnosis of MPM in an overwhelming majority of patients in the LTS group. An epithelial subtype of MPM behaving clinically more indolently seems to exist, but further tumor and genetic characterization is needed. The prolonged survival time is most likely explained by a combination of tumor-, patient-, and treatment-related factors.

Copyright © 2020 Elsevier Inc. All rights reserved.

In plain English

This retrospective Finnish study examined malignant pleural mesothelioma patients who lived more than 5 years after diagnosis. The authors started from a national cohort of 1010 patients diagnosed in 2000-2012. Experts re-reviewed tissue samples of the survivors and of a comparison group of epithelial-subtype patients from the Helsinki region. Of 52 patients first identified as surviving over 5 years, one was misdiagnosed. Two localized malignant mesotheliomas and two well-differentiated papillary mesotheliomas were also found and excluded. The 43 confirmed long-term survivors were compared with 84 controls. Survivors were younger, more often women and in better condition at diagnosis. Fewer survivors had a recognized occupational asbestos disease (42% versus 75%). Among those tested, survivors' median lung asbestos fiber count was lower (0.4 versus 9.0 million fibers per gram of dry lung). After adjustment, surgery, chemotherapy, better performance status and smaller tumors were associated with longer survival. Occupational disease was significant only before adjustment. The authors concluded that long survival was not explained by diagnostic error but by tumor-, patient- or treatment-related factors. They listed the retrospective design and missing BAP1 gene information among the limitations.

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: Retrospective comparison of long-term survivors (more than 5 years) with a control group of epithelial mesothelioma patients, with blinded re-review of pathology samples and CT scans, and survival (Cox regression) analysis
• Who was studied: From a cohort of 1010 patients diagnosed with malignant pleural mesothelioma in Finland in 2000-2012 (Finnish Cancer Registry): 43 long-term survivors with overall survival over 5 years, compared with 84 patients with epithelial mesothelioma from the Hospital District of Helsinki and Uusimaa diagnosed in 2007-2012
• Exposure: Asbestos exposure assessed from medical records (self-reported exposure), workers' compensation decisions for occupational asbestos disease, lung asbestos fiber counts by scanning transmission electron microscopy, and pleural plaques on CT. No fiber types are named. Treatments (surgery, chemotherapy, radiotherapy) were also studied.
• Main results:
  • Of the 52 patients first identified with overall survival over 60 months, one had an incorrect mesothelioma diagnosis (an adenocarcinoma misclassified as mesothelioma). The article reports this as 0.5%, which matches all 213 reviewed patients (52 potential survivors plus 161 potential controls), not the survivor group alone. Two localized malignant mesotheliomas and two well-differentiated papillary mesotheliomas were also found among the 52 and excluded.
  • Compared with controls, long-term survivors were younger (median age 61.0 vs 67.30 years), more often female (13, 30.2% vs 10, 11.9%), and had better performance status at diagnosis (ECOG 0: 39, 90.7% vs 33, 39.3%).
  • Occupational asbestos disease was determined in 18 long-term survivors (42%) vs 63 controls (75%), p<0.001. Self-reported asbestos exposure was found in 19 long-term survivors (44%) vs 64 controls (76%), p<0.001.
  • Fiber analysis was done for 13 long-term survivors (30%) and 60 controls (71%). Median lung fiber content was 0.4 (IQR 0.2 to 5.4) million fibers per gram of dry lung in long-term survivors vs 9.0 (IQR 0.6 to 132.5) in controls, p=0.019.
  • Bilateral pleural plaques were seen in 16 long-term survivors (42.1%) vs 52 controls (62.7%), p=0.034.
  • In the adjusted Cox model, surgery (HR 0.39, 95% CI 0.21-0.73) and chemotherapy (HR 0.47, 95% CI 0.27-0.83) were associated with better overall survival. ECOG performance status I-III was associated with worse survival (HR 2.97, 95% CI 1.82-4.82). Tumor size also had an impact (HR 1.01, 95% CI 1.00-1.01).
  • Asbestos-related occupational disease was associated with survival only in crude analysis (unadjusted HR 1.70, 95% CI 1.15-2.50). It was not significant after adjustment (HR 1.29, 95% CI 0.78-2.16, p=0.314).
  • In the long-term survivor group, two patients had a first-degree relative with mesothelioma. Two had received lymphoma-related radiation therapy over 15 years before diagnosis. No control had prior therapeutic intrathoracic radiation.
• The authors' conclusion: The authors concluded that prolonged survival in malignant pleural mesothelioma was not explained by diagnostic error but by tumor-, patient- or treatment-related factors. They found tumor size, ECOG performance status and first-line treatment (surgery and chemotherapy) associated with survival time. They suggested a more indolent epithelial subtype may exist.
• Limitations the authors state:
  • Retrospective design.
  • BAP1 information was unavailable and is a possible confounding factor in the survival analyses.
  • One-third of tumor samples were small, which can complicate diagnosis.
  • Lead-time bias cannot be ruled out.
  • Asbestos fiber analyses were done in unequal proportions in the two groups.
  • Treatment effects on survival could be confounded by patient-driven factors in a non-randomized setting.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Asbestos Exposure, Overall Survival, Localized Malignant Mesothelioma, Well-Differentiated Papillary Mesothelioma, Performance Status, Multivariate Analysis, Chemotherapy.

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