Prognostic role of radiological peritoneal cancer index in malignant peritoneal mesothelioma: national cohort study

Our plain-English summary of Prognostic role of radiological peritoneal cancer index in malignant peritoneal mesothelioma: national cohort study, by S.A.S. Salo, E. Lantto, E. Robinson, et al (Scientific Reports, 2020).

The study

• Authors: S.A.S. Salo, E. Lantto, E. Robinson, M. Myllärniemi, S. Laaksonen, J.A. Salo, T. Rantanen, I. Ilonen
• Journal: Scientific Reports
• Published: 2020;10(1):13257
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant peritoneal mesothelioma (MPeM) is a rare cancer of the mesothelial cells of the peritoneum. Computed tomography (CT) is considered the standard for first-line imaging of MPeM, diagnosis and risk stratification remains challenging. Peritoneal cancer index (PCI), as assessed by CT, is utilized in the prognostic assessment of other malignant intra-abdominal conditions; however, there is limited data concerning the utility of PCI in the diagnosis and workup of MPeM. We studied a retrospective cohort of all patients diagnosed with MPeM from 2000 to 2012 in Finland. CT and magnetic resonance imaging (MRI) were reviewed and scored by an experienced and blinded, board-certified abdominal radiologist. Additional clinical data and outcomes were obtained from Finnish Cancer Registry (FCR), the Workers' Compensations Center (WCC), and Statistics Finland (SF). Abdominal CT or MRI was available for 53 of 90 patients. The median radiographic PCI was 25. PCI score was correlated with overall survival (p = 0.004, Exp(B) = 1.064, 95% CI 1.020-1.110). PCI score ≥ 30 was associated with worse survival (p = 0.002), while PCI ≤ 19 was associated with improved overall survival (p = 0.001). Our study indicates that radiological PCI is prognostic in MPeM and should be assessed during radiographic workup and integrated into clinical decision-making.

In plain English

This retrospective national cohort study from Finland asked whether a CT-based score of how widely cancer had spread in the abdomen, the peritoneal cancer index (PCI, scored 0 to 39 across 13 regions), is related to survival in malignant peritoneal mesothelioma. All 90 patients diagnosed in Finland from 2000 to 2012 were identified through the Finnish Cancer Registry. Abdominal CT or MRI was available for 53 of them (38 men, 15 women). One radiologist, who knew the diagnosis but not the original reports or clinical details, scored the images. The median PCI was 25. A higher PCI was associated with worse overall survival. The text reports a median survival of 43 months for patients scoring 0 to 19 (17 patients) and 6 months for those scoring 20 to 39 (36 patients), while a table gives 57 and 12 months. PCI was not significantly associated with asbestos exposure (p = 0.252). Exposure information came from the Workers' Compensation Center, and no fiber types were reported. The authors concluded that radiological PCI has prognostic value. They noted the small number of patients, missing treatment records and harder-to-read older CT images.

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 population-based (national) cohort study using registry data and re-reading of CT/MRI images
• Who was studied: All 90 patients diagnosed with primary malignant peritoneal mesothelioma in Finland from 1 January 2000 to 31 December 2012, identified through the Finnish Cancer Registry. The 53 with abdominal CT or MRI available (38 men, 15 women) formed the final study population.
• Exposure: The main factor studied was the radiological peritoneal cancer index (disease spread on imaging), not asbestos. Asbestos exposure data came from the Workers' Compensations Center. In Table 2, 15 of 53 patients (28.3%) were recorded as exposed, 27 as not exposed and 11 as unknown. No fiber types, jobs or doses were reported.
• Main results:
  • Across all 53 imaged patients, a higher PCI score was associated with worse overall survival. The body text gives p = 0.04. The article's own abstract gives p = 0.004, Exp(B) = 1.064, 95% CI 1.020 to 1.110.
  • In the text, median survival was 43 months (range 2 to 192) in the low PCI group (0 to 19; 17 of 53 patients) and 6 months (range 0 to 92) in the high PCI group (20 to 39; 36 of 53 patients), p = 0.001 by Cox regression. Table 3 instead lists 57 months (2 to 192) and 12 months (0 to 92).
  • Low PCI group survival: 1-year 58.8% (10/17), 2-year 52.9% (9/17) and 5-year 23.5% (4/17).
  • High PCI group survival: 1-year 22.2% (8/36), 2-year 8.3% (3/36) and 5-year 5.6% (2/36).
  • PCI score was not significantly associated with ascites (p = 0.082), lymph node or extra-abdominal metastases (p = 0.295), pleural effusion (p = 0.240) or asbestos exposure (p = 0.252).
  • Median PCI was 25 (range 0 to 36) among patients with asbestos exposure (printed as 'asbestosis exposure') and 25 (range 0 to 39) among patients with no suspected occupational exposure.
  • Patients with ascites had a median survival of 7 months versus 39 months for patients without ascites. This difference was not statistically significant (p greater than 0.05).
• The authors' conclusion: The authors concluded that the radiological peritoneal cancer index has significant prognostic value in malignant peritoneal mesothelioma, and that grouping patients by PCI meaningfully separated them by survival after diagnosis.
• Limitations the authors state:
  • The number of patients was small.
  • Information on treatment response was partly scarce because some medical records had been removed for privacy protection after 10 years of storage.
  • Older CT images had wider cross-sections, which made assessing the bowel surface and diaphragm more difficult.
  • Surgical PCI was not studied because only a minority of patients had surgery.
  • Survival differed significantly between imaged and non-imaged patients. The authors attributed this to most non-imaged patients being diagnosed at autopsy.
  • Lymph node spread could not be confirmed pathologically in most cases, so the lymph node findings may be biased by relying on imaging alone.
  • The study was likely underpowered to detect a survival difference by ascites.

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Cancer Index (PCI), Peritoneal Mesothelioma, Cohort Study, Mesothelial Cells, Peritoneum, Cancer Registry, Overall Survival.

Related studies

• Malignant Peritoneal Mesothelioma: Treatment Options and Survival — S.A.S. Salo, I. Ilonen, et al. (2019)
• Epidemiology of malignant peritoneal mesothelioma: A population-based study — S.A.S. Salo, I. Ilonen, et al. (2017)
• Prognostic significance of morphological growth patterns and mitotic index of epithelioid malignant peritoneal mesothelioma — A.M. Krasinskas, A.C. Borczuk, et al. (2016)
• Recurrent malignant peritoneal mesothelioma: radiological manifestations — F.F. Souza, J. Jagganathan, et al. (2010)
• Prognostic nutritional index predicts outcomes of malignant pleural mesothelioma — Z.H. Yao, G.Y. Tian, et al. (2013)
• Malignant Peritoneal Mesothelioma: National Practice Patterns, Outcomes, and Predictors of Survival — V. Verma, R.L. Sleightholm, et al. (2018)

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