Computed tomography in the evaluation of malignant pleural mesothelioma-Association of tumor size to a sarcomatoid histology, a more advanced TNM stage and poor survival

Our plain-English summary of Computed tomography in the evaluation of malignant pleural mesothelioma-Association of tumor size to a sarcomatoid histology, a more advanced TNM stage and poor survival, by J. Paajanen, S. Laaksonen, I. Ilonen, et al (Lung Cancer, 2018).

The study

• Authors: J. Paajanen, S. Laaksonen, I. Ilonen, H. Wolff, K. Husgafvel-Pursiainen, E. Kuosma, H. Ollila, M. Myllärniemi, T. Vehmas
• Journal: Lung Cancer
• Published: 2018;116:73-79
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Appropriate clinical staging of malignant pleural mesothelioma (MPM) is critical for correct treatment decisions. Newly revised TNM staging protocol has been released for MPM. We investigated baseline computed tomography (CT) characteristics of MPM patients, the new staging system and a simple tumor size (TS) assessment in terms of survival.

Materials And Methods: As part of our study that included all MPM patients diagnosed in Finland 2000-2012, we retrospectively reviewed 161 CT scans of MPM patients diagnosed between 2007 and 2012 in the Hospital District of Helsinki and Uusimaa. TS was estimated by using the maximal tumor thickness and grading tumor extension along the chest wall. Cox Regression models were used to identify relationships between survival, clinicopathological factors and CT-findings.

Results: The median length of follow-up was 9.7 months and the median survival 9.1 months. The right sided tumors tended to be more advanced at baseline and had worse prognosis in the univariate analyses. In the multivariate survival model, TS, pleural effusion along with non-epithelioid histology were predictors of poor survival. Tumor size correlated significantly with a sarcomatoid histopathological finding and several parameters linked to a more advanced TNM stage. Most patients were diagnosed with locally advanced stage, while 12 (7%) had no sign of the tumor in CT.

Conclusion: In this study, we demonstrate a novel approach for MPM tumor size evaluation that has a strong relationship with mortality, sarcomatoid histology and TNM stage groups. TS could be used for prognostic purposes and it may be a useful method for assessing therapy responses.

Copyright © 2018 Elsevier B.V. All rights reserved.

In plain English

This retrospective cohort study, part of a Finnish project on malignant pleural mesothelioma (MPM) diagnosed in 2000–2012, reviewed computed tomography (CT) scans of 161 patients diagnosed between 2007 and 2012 in the Hospital District of Helsinki and Uusimaa. One radiologist staged the tumors with the new 8th-edition TNM system. The radiologist also calculated a 'tumor size' score by multiplying the tumor's maximal thickness by a grade for how far it extended around the chest. Median survival was 9.1 months. Twelve patients (7%) had no recognizable tumor on CT. Tumor size was largest in the sarcomatoid subtype and correlated with TNM stage. After adjustment, larger tumor size, more pleural fluid and non-epithelioid histology were linked to poorer survival. For sarcomatoid versus epithelioid tumors the hazard ratio was 4.71 (95% CI 2.88–7.69). TNM stage was not independently associated with survival. The authors concluded that their tumor size method was strongly related to mortality, sarcomatoid histology and stage. They named the retrospective design and the single reader as 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 cohort study (review of CT scans at diagnosis, with survival follow-up)
• Who was studied: 161 patients with malignant pleural mesothelioma diagnosed 2007–2012 in the Hospital District of Helsinki and Uusimaa, Finland, who had CT scans available at diagnosis. They were drawn from 1010 patients in the Finnish Cancer Registry. 138 (86%) were male and the median age was 68.7 years. Survival follow-up closed on February 17, 2017.
• Exposure: The study examined CT findings, not asbestos dose. Asbestos exposure was recorded only as whether the patient had a compensated occupational disease due to asbestos at work, according to the Finnish Workers' Compensation Center. This applied to 109 patients (68%). No fiber types are given.
• Main results:
  • Median length of follow-up was 9.7 months. Median survival of the 161-patient cohort was 9.1 months. Six (4%) patients were alive at the end of the study period.
  • The most common CT findings were pleural thickening, in 149 (93%) patients, and pleural effusion, in 144 (89%).
  • 12 (7%) patients had no distinct tumor findings on CT and were diagnosed from a surgical pleural biopsy.
  • Tumor size differed by histological subtype (p = 0.003). Median tumor size was 66 in sarcomatoid, 33 in epithelioid and 16 in biphasic tumors.
  • Tumor size correlated with TNM T-class (r = 0.70), N-class (0.41) and stage (0.69), each with p less than 0.0001.
  • In the adjusted Cox model, sarcomatoid histology had a hazard ratio of 4.71 (95% CI 2.88–7.69) compared with epithelioid. Tumor size and pleural effusion (both continuous) were also independent predictors of poor survival, each with p less than 0.001.
  • In the adjusted Cox model, biphasic histology had a hazard ratio of 2.07 (95% CI 1.27–3.38) compared with epithelioid.
  • TNM stage was suggestively associated with mortality in univariate analysis (p = 0.075) but not after multivariate adjustment (p = 0.225).
  • Patients were split into three tumor-size groups (low 0–11, middle 12–79, high 80–306). Median survival was 14.0 months in the lowest group, 11.1 months in the middle group and 5.4 months in the highest group. Survival in the lowest group was significantly higher than in the other groups (p = 0.016).
  • Median survival was 6.3 months in TNM stage IV and 24.1 months in stage 0. There was no difference between stage groups I to III (p = 0.776).
  • Pleural calcification was associated with poorer survival in univariate analysis (hazard ratio 1.39, 95% CI 1.01–1.91). After adjustment the hazard ratio was 1.22 (95% CI 0.84–1.78, p = 0.298). Bilateral pleural plaques were seen in 99 (62%) patients and bilateral calcification in 74 (46%).
  • A compensated occupational disease was not associated with survival (unadjusted hazard ratio 0.95, 95% CI 0.67–1.33, p = 0.744).
• The authors' conclusion: The authors concluded that their new tumor size evaluation has a strong relationship with mortality, sarcomatoid histology and TNM stage groups. They suggested it could be used to refine prognostic evaluation, said further studies are needed on its use for treatment responses, and found that non-epithelioid histology and the amount of pleural effusion were independent markers of worse prognosis.
• Limitations the authors state:
  • The retrospective design.
  • Variability in CT imaging (different scanners and protocols across hospitals) can affect measurements.
  • Splitting patients into many TNM groups leaves little statistical power.
  • Only one radiologist read the scans, so agreement between different readers was not measured.
  • Repeat readings by the same radiologist agreed less well for the emphysema scale and for metastasis.
  • The pleural effusion measurement can be biased by previous thoracentesis (fluid drainage), although the authors tried to adjust for this.
  • Lung fibrosis and emphysema were mostly absent or minor, which limited the power to show any association with outcome.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Sarcomatoid, Histology, Staging, TNM Staging, CT Scan, Median Survival, Prognosis.

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• A new prognostic index for overall survival in malignant pleural mesothelioma: the rPHS (regimen, PS, histology or stage) index — Y. Kataoka, Y. Yamamoto, et al. (2015)
• Clinical Features in Patients With Malignant Pleural Mesothelioma With 5-Year Survival and Evaluation of Original Diagnoses — J. Paajanen, S. Laaksonen, et al. (2020)
• B7-H1 expression in malignant pleural mesothelioma is associated with sarcomatoid histology and poor prognosis — A.S. Mansfield, A.C. Roden, et al. (2014)
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