The revised staging system for malignant pleural mesothelioma based on surveillance, epidemiology, and end results database

Our plain-English summary of The revised staging system for malignant pleural mesothelioma based on surveillance, epidemiology, and end results database, by S. Wang, K. Ma, Q. Wang, et al (International Journal of Surgery, 2017).

The study

• Authors: S. Wang, K. Ma, Q. Wang, F. Sun, Y. Shi, C. Zhan, W. Jiang
• Journal: International Journal of Surgery
• Published: 2017;48:92-98
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Several staging systems for MPM have been introduced. However, none of them provide perfect survival stratification among heterogeneous patients. The aim of this population-based cohort study was to propose adjustments to current staging system for malignant pleural mesothelioma (MPM).

Methods: We retrieved MPM data from Surveillance, Epidemiology, and End Results database (1973-2014). Kaplan-Meier method was derived to examine the prognostic effects of tumor, lymph node, metastasis and histology features. Proportional hazards models guided adjustments to stage groupings. The accuracy of staging systems at predicting survival was evaluated by concordance index and bootstrap resampling.

Results: A total of 1110 MPM cases were extracted from SEER. T stage failed to demonstrate survival difference between adjacent categories with the exception of T3 versus T4 (P < 0.001). Patients in M0 had better prognosis than those in M1 (P < 0.001). Exploratory analyses suggested important survival difference for single-versus multiple-site M1 cases (P < 0.001), but not for different metastatic sites (P = 0.286). Histology subtype was a significant prognostic indicator (P < 0.001). Regrouping of TNM and histology combinations resulted in the best concordance index (0.683), compared with UICC 2010 (0.578) and IASLC 2016 (0.585) staging systems. The revised staging system also improved patients distribution (IA:33.8%, IB:17.0%, II: 20.7%, IIIA:10.6%, IIIB: 6.8%, IV:11.1%). Log-rank analyses and calibration plots both demonstrated the new stage achieved optimal survival prediction and discrimination.

Conclusion: The revised staging system improved patients distribution and survival stratification for MPM.

Copyright © 2017 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.

In plain English

This study used United States SEER cancer database records to revise the staging system for malignant pleural mesothelioma (MPM). Staging is the way doctors group patients by how far the cancer has spread. Only 1110 patients, all diagnosed from 2010 to 2014, met the study criteria. Tumor (T) stage categories describe how far the main tumor extends; they did not separate survival between neighbouring categories, except T3 versus T4. Lymph-node spread showed no significant survival difference. Patients whose cancer had spread to distant sites had worse survival. Tissue type also mattered: median survival was 14.0 months for epithelioid, 10.0 for biphasic and 5.0 for sarcomatoid MPM. The authors built a revised system that adds tissue type and places sarcomatoid cases in stage IIIB or IV. Its accuracy score (c-index) was 0.683 (95% CI 0.671 to 0.695), versus 0.578 (0.566 to 0.590) for the UICC 2010 system and 0.585 (0.573 to 0.597) for IASLC 2016. The authors concluded the revised system improved survival grouping, and said larger prospective studies must confirm it. The study did not look at asbestos exposure.

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: Population-based retrospective cohort study using a national cancer registry database (SEER), analysed with survival statistics to propose a revised staging system
• Who was studied: 1110 patients with malignant pleural mesothelioma recorded in the US National Cancer Institute's SEER database. The database was searched for 1973 to 2014, but all patients diagnosed before 2010 were excluded, so the cases were diagnosed 2010 to 2014. The group was 860 men (77.5%) and 250 women (22.5%), with a median age of 72 years; 91.4% were white.
• Exposure: Not studied. The article reports no information on asbestos or any other exposure; it examined tumor stage (T, N, M categories) and tissue type (epithelioid, biphasic, sarcomatoid).
• Main results:
  • In all patients, tumor (T) stage categories, which describe the local extent of the main tumor, failed to show a survival difference between neighbouring categories, except T3 versus T4 (P < 0.001; hazard ratio 1.613, 95% CI 1.343 to 1.937).
  • Patients with lymph-node involvement (N1 to N3, analysed together) did not have significantly different survival from patients with N0 disease (HR 1.107; 95% CI 0.960 to 1.276; P = 0.150).
  • The 948 patients without distant spread (M0) had better survival than the 162 patients with distant spread (M1) (HR for M1 1.934; 95% CI 1.602 to 2.334; P < 0.001).
  • Among patients with distant spread, survival did not differ significantly by site (bone, brain, liver or lung; P = 0.286). Median survival was 4.0, 2.0, 4.0 and 4.0 months, respectively.
  • Among patients with distant spread, survival for single-site spread (65 patients) differed significantly from multiple-site spread (25 patients). Table 1 gives HR 2.216 (95% CI 1.335 to 3.679), P 0.002, for multiple sites. The text gives different figures (see text problems).
  • Tissue type was a significant predictor of survival (P < 0.001). The 3-year overall survival was 15.9% for epithelioid, 9.3% for biphasic and 0.0% for sarcomatoid MPM. Median survival was 14.0, 10.0 and 5.0 months, respectively.
  • In the revised system, which combines TNM stage with tissue type, sarcomatoid cases were placed in stage IIIB or stage IV.
  • In the revised system, median survival was 17, 13, 12, 8, 6 and 5 months for stages IA, IB, II, IIIA, IIIB and IV. Two-year survival was 36.5%, 27.0%, 18.9%, 11.7%, 5.1% and 3.5%. Patients were spread across stages as 33.8%, 17.0%, 20.7%, 10.6%, 6.8% and 11.1%.
  • The c-index (an accuracy score where higher means better survival prediction) was 0.578 (95% CI 0.566 to 0.590) for the UICC 2010 system, 0.585 (95% CI 0.573 to 0.597) for the IASLC 2016 system, and 0.683 (95% CI 0.671 to 0.695) for the revised system.
• The authors' conclusion: The authors concluded that their revised staging system, which combines TNM stage and tissue type, improved how well patients were grouped by survival. They said a larger, prospective study is needed to validate it.
• Limitations the authors state:
  • Some information was not recorded or not available in the SEER database.
  • The study did not assess how well treatments worked, because there was no randomized clinical trial.
  • The new system differs substantially from earlier ones, and the authors stated that a larger, prospective study is needed to validate it.
  • SEER recorded clinical rather than pathological stage for patients who had treatment before surgery or no surgery, which may make T stage inaccurate. The number of T1 cases was also limited.

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: Staging, Pleural Mesothelioma, Epidemiology, Cohort Study, Metastasis, Histology, Stage Grouping, Concordance Index.

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