Does size matter? -a population-based analysis of malignant pleural mesothelioma

Our plain-English summary of Does size matter? -a population-based analysis of malignant pleural mesothelioma, by J. He, S. Xu, H. Pan, et al (Translational Lung Cancer Research, 2020).

The study

• Authors: J. He, S. Xu, H. Pan, S. Li, J. He
• Journal: Translational Lung Cancer Research
• Published: 2020;9(4):1041-1052
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The 8th edition staging system for malignant pleural mesothelioma (MPM) has been proposed. The size of tumor is not taken into consideration. We intend to elucidate the prognostic value of the size of MPM and evaluate the current staging system via the data of SEER database.

Methods: All cases of primary MPM were identified and extracted from the SEER database during the period of 2004-2016. The endpoints were overall survival (OS) and cancer-specific survival (CSS) which were analyzed using Kaplan-Meier method. Log-rank test and Cox regression were utilized to identify the prognostic factors.

Results: A total of 2,138 patients were included in the primary cohort. The 1-, 3- and 5-year survival rates of MPM were 39.4%, 11.8% and 3.8%. Older, male and advanced stage patients accounted for larger proportion of the cohort. Besides tumor extension, lymph node involvement and metastatic status, tumor size, pathological type and differentiation grade were significant prognostic factors. In the stratified analysis of tumor extension, size is a significant prognostic factor in T2 patients and indicates inferior survival outcomes. Surgery, chemotherapy and radiation can increase both OS and CSS in MPM patients. Triple combination treatments showed a superiority to other treatments.

Conclusions: Tumor size matters in the prognosis of MPM especially in the early stage of MPM patients. The adjusted TNM staging system incorporating tumor size has better accuracy than the 8th edition IMIG system. However, some stages had not been fully identified. More cases of early stages are warranted for essential revision.

2020 Translational Lung Cancer Research. All rights reserved.

In plain English

This study used US SEER cancer registry records to ask whether tumor size affects survival in malignant pleural mesothelioma. Of 11,736 patients with this cancer in the database, 2,138 had the tumor size and spread data the analysis required. The study did not examine asbestos exposure. In this group, 39.4% were alive after 1 year, 11.8% after 3 years and 3.8% after 5 years. Larger tumors were linked to shorter survival after other factors were accounted for. When patients were grouped by tumor spread, size was significantly linked to survival only in the second group (E2); in the others the link was not significant. There, median survival was 19 months for tumors 3 cm or smaller, 12 months for 3 to 7 cm, and 8 months for over 7 cm. The authors proposed a revised staging system that adds tumor size. It matched actual survival better than the 8th and 7th editions (concordance 0.61 versus 0.58 and 0.54). The authors concluded that size matters, especially in early-stage disease. They noted that early-stage patients were few and much incomplete data was excluded.

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 analysis of cancer registry data (SEER database), using survival analysis and Cox regression
• Who was studied: 2,138 patients with primary malignant pleural mesothelioma, drawn from 11,736 pleural mesothelioma patients in the US SEER 18 registries. Patients were excluded if tumor data, tumor extension or tumor size was unknown. Other information, such as differentiation grade, was still unknown for many included patients. The abstract gives the diagnosis period as 2004 to 2016. Mean age was 69.02 years, 1,681 were male, and 91.1% were white.
• Exposure: Not studied. The factors analyzed were tumor size, tumor extension, lymph node involvement, metastasis, histology, grade, patient characteristics and treatments (surgery, chemotherapy, radiation). Asbestos is mentioned only as background, citing other work.
• Main results:
  • In the main group of 2,138 patients, overall survival was 39.4% at 1 year, 11.8% at 3 years and 3.8% at 5 years.
  • Tumor size was an independent factor linked to worse survival. The multivariate hazard ratio was 1.002 per mm (95% CI 1.001 to 1.003, P less than 0.001).
  • By tumor extension subgroup, size had a statistically significant effect on survival only in the E2 group. It was not significant in the E1, E3 or E4 groups. The authors did not show these data.
  • In E2 patients, median survival was 19 months for tumors 3 cm or smaller, 12 months for 3 to 7 cm, and 8 months for larger than 7 cm (P=0.015).
  • The C-index (how well staging matched actual survival) was 0.61 for the authors' adjusted staging system, 0.58 for the 8th edition IMIG system and 0.54 for the 7th edition. The difference was P less than 0.0001.
  • Female patients had better survival than male patients (univariate HR 0.724, 95% CI 0.647 to 0.81).
  • In multivariate analysis, surgery and chemotherapy were independent prognostic factors but radiation was not. Patients given triple combination treatment had a median survival of 23 months, compared with 5 months for those given no treatment.
• The authors' conclusion: The authors concluded that, besides tumor extension, lymph node involvement and metastasis, tumor size matters in outcomes, especially in early-stage malignant pleural mesothelioma. They found that their adjusted staging system with tumor size predicted survival better, and called for a larger cohort with complete data to verify this.
• Limitations the authors state:
  • SEER provides no radiographic (scan) or blood-test data, so clinical staging and image assessment could not be studied.
  • A large amount of incomplete data was excluded.
  • Early-stage patients were a small part of the cohort, so analyses of them may be inconclusive.
  • Cases with multifocal lesions could not be identified.
  • The lack of data on surgical approach and other illnesses (comorbidities) left the comparison between surgery types (P/D versus EPP) unclear.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Staging, SEER, Overall Survival, Chemotherapy, Prognosis, TNM Staging, IMIG.

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