Implementing CT tumor volume and CT pleural thickness into future staging systems for malignant pleural mesothelioma

Our plain-English summary of Implementing CT tumor volume and CT pleural thickness into future staging systems for malignant pleural mesothelioma, by O. Lauk, M. Patella, T. Neuer, et al (Cancer Imaging, 2021).

The study

• Authors: O. Lauk, M. Patella, T. Neuer, B. Battilana, T. Frauenfelder, T.D.L. Nguyen-Kim, W. Weder, C. Caviezel, S. Hillinger, I. Inci, I. Opitz
• Journal: Cancer Imaging
• Published: 2021;21(1):48
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: Tumor thickness and tumor volume measured by computed tomography (CT) were suggested as valuable prognosticator for patients' survival diagnosed with malignant pleural mesothelioma (MPM). The purpose was to assess the accuracy of CT scan based preoperatively measured tumor volume and thickness compared to actual tumor weight of resected MPM specimen and pathologically assessed tumor thickness, as well as an analysis of their impact on overall survival (OS).

Methods: Between 09/2013-08/2018, 74 patients were treated with induction chemotherapy followed by (extended) pleurectomy/decortication ((E)PD). In 53 patients, correlations were made between CT-measured volume and -tumor thickness (cTV and cTT) and actual tumor weight (pTW) based on the available values. Further cTV and pT/IMIG stage were correlated using Pearson correlation. Overall survival (OS) was calculated with Kaplan Meier analysis and tested with log rank test. For correlation with OS Kaplan-Meier curves were made and log rank test was performed for all measurements dichotomized at the median.

Results: Median pathological tumor volume (pTV) and pTW were 530 ml [130 ml - 1000 ml] and 485 mg [95 g - 982 g] respectively. Median (IQR) cTV was 77.2 ml (35.0-238.0), median cTT was 9.0 mm (6.2-13.7). Significant association was found between cTV and pTV (R = 0.47, p < 0.001) and between cTT and IMIG stage (p = 0,001) at univariate analysis. Multivariate regression analysis revealed, that only cTV correlates with pTV. Median follow-up time was 36.3 months with 30 patients dead at the time of the analysis. Median OS was 23.7 months. 1-year and 3-year survival were 90 and 26% respectively and only the cTV remained statistically associated with OS.

Conclusion: Preoperatively assessed CT tumor volume and actual tumor volume showed a significant correlation. CT tumor volume may predict pathological tumor volume as a reflection of tumor burden, which supports the integration of CT tumor volume into future staging systems.

© 2021. The Author(s).

In plain English

This retrospective study at University Hospital Zurich reviewed patients with malignant pleural mesothelioma treated from September 2013 to August 2018 with chemotherapy followed by (extended) pleurectomy/decortication. Of 74 such patients, 53 had complete data. The authors compared CT-measured tumor volume and thickness before surgery with the volume of the removed tissue, with pathological stage, and with survival. Specimen weight was left out because it closely matched volume. Asbestos exposure was recorded as yes for 26, possible for 10 and no for 17 patients. Median CT tumor volume was 77.2 ml. The removed specimens, which included diaphragm and pericardium in 49 patients, had a median volume of 530 ml. CT volume was significantly associated with specimen volume. CT thickness was associated with stage but added no information for predicting specimen volume once CT volume was known. Median survival was 23.7 months (95% confidence interval 17.9 to 34 months), and only CT volume remained statistically associated with survival. The authors concluded that CT tumor volume may reflect tumor burden and could help improve staging, but said their results lack the power to propose a staging change.

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 analysis of CT scans and clinical and pathological records at a single institution (surgical cohort)
• Who was studied: Patients with malignant pleural mesothelioma at University Hospital Zurich, September 2013 to August 2018. 74 had induction chemotherapy followed by (extended) pleurectomy/decortication, and 53 of them had all measurements available for analysis.
• Exposure: The study did not examine asbestos exposure as a cause. What it measured was CT-derived tumor thickness (cTT) and tumor volume (cTV) on the scan taken after chemotherapy and before surgery. These were compared with the measured volume of the removed specimen, with pathological stage, and with survival. No asbestos fiber types are reported.
• Main results:
  • Specimen weight and specimen volume were very highly correlated (Pearson r = 0.94, p less than 0.001), so only specimen volume was kept in the analysis.
  • Recorded asbestos exposure among the 53 patients: no in 17 (32.1%), possible in 10 (18.9%), yes in 26 (49.1%).
  • Removed specimens (53 patients): median pathological tumor volume 530 ml (range 130 to 1000 ml).
  • Removed specimens (53 patients): median tumor weight 485 g (range 95 to 982 g), according to Table 2.
  • CT measurements (53 patients): median CT tumor volume 77.2 ml (interquartile range 35.0 to 238.0) and median CT tumor thickness 9.0 mm (6.2 to 13.7).
  • In univariate analysis, CT tumor volume was significantly associated with pathological tumor volume (p less than 0.001), and CT tumor thickness with IMIG stage (p = 0.001).
  • In multivariate analysis, only CT tumor volume remained correlated with pathological tumor volume. CT tumor thickness added no further information once CT volume was known (p = 0.21).
  • Survival: median follow-up was 36.3 months, and 30 patients had died at the time of analysis. Median overall survival was 23.7 months (95% CI 17.9 to 34 months).
  • Survival: 1-year survival was 90% and 3-year survival was 26%.
  • In Cox models of survival, CT tumor volume was the only one of four measures (CT volume, CT thickness, pathological volume, IMIG stage) that remained statistically significant (HR 1.002, p = 0.02).
  • Only the model with the CT-based (clinical) measures improved significantly on a model with no covariates (p = 0.003). The authors said this suggests the CT measures fit survival better than the pathological ones.
• The authors' conclusion: The authors concluded that their study supports the prognostic relevance of tumor burden. They described a high correlation between CT tumor volume before surgery and the actual volume of the removed specimen, and said CT volume could help improve future staging systems.
• Limitations the authors state:
  • Retrospective design carries an inherent bias.
  • Only surgically treated patients were included.
  • CT thickness measurements were not available at all three levels for some patients. At least two levels were required, which may make the thickness value less representative.
  • Comparing CT volume with specimen volume is difficult because the specimens were much larger: they included resected diaphragm and pericardium in extended surgery.
  • Small sample size, given as one possible reason why CT thickness showed no prognostic significance.
  • The results lack the statistical power to propose a change in the staging system.

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 Thickening, Staging, Pleural Mesothelioma, CT Scan, Overall Survival, Chemotherapy, Pleurectomy/Decortication (P/D), IMIG.

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