Trends in Pleural Mesothelioma Incidence and Survival in Metropolitan and Nonmetropolitan Areas in the United States

Our plain-English summary of Trends in Pleural Mesothelioma Incidence and Survival in Metropolitan and Nonmetropolitan Areas in the United States, by A.J. Didier, C. Lennox, M. Li, et al (Cancer Medicine, 2025).

The study

• Authors: A.J. Didier, C. Lennox, M. Li, J. Gheeya, A. Alahmadi, J. Kaufman, R. Memmott, K. He, P. Shields, C. Rolfo, D.P. Carbone, C. Presley, D. Owen, L. Roof
• Journal: Cancer Medicine
• Published: 2025;14(24):e71474
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Pleural mesothelioma (PM) is a rare, aggressive cancer with significant variation in incidence based on geographic factors. Previous studies have highlighted cancer survival disparities between metropolitan and nonmetropolitan populations for other cancers; this data is largely unreported for PM. We aimed to compare incidence trends and cancer-specific survival (CSS) between metropolitan and nonmetropolitan areas in the United States using the Surveillance, Epidemiology, and End Results (SEER) database.

Methods: We analyzed SEER 18 registries for patients aged ≥ 20 diagnosed with PM between 2004 and 2021. Incidence rates, CSS, and demographic and clinical characteristics were compared between metropolitan and nonmetropolitan areas. Incidence rate ratios (IRRs) were calculated using the Tiwari method. Joinpoint regression was used to assess temporal trends, while Kaplan-Meier and Cox proportional hazard models analyzed survival outcomes.

Results: A total of 8519 PM cases were identified, with 89.3% in metropolitan areas. Nonmetropolitan patients were more likely to be non-Hispanic Black and had lower chemotherapy (p = 0.031) and surgery (p < 0.001) rates. The incidence rate in metropolitan areas declined from 1.4 in 2004 to 0.8 in 2021, while nonmetropolitan areas saw a stable incidence until 2017, followed by a decline to 0.5 in 2021. Metropolitan areas had significantly higher CSS, with 50.3% 1-year CSS by 2020, compared to 27.7% in nonmetropolitan areas. Multivariate analysis indicated a higher hazard of death in nonmetropolitan areas (HR = 1.18, p < 0.001).

Conclusion: Significant disparities in PM outcomes between metropolitan and nonmetropolitan areas were revealed. Although both regions experienced a decline in incidence over time, survival outcomes remained worse in nonmetropolitan areas. Patients in nonmetropolitan areas were also less likely to receive chemotherapy and surgery, further contributing to the survival gap. These findings highlight the need for targeted interventions to improve treatment access and enhance survival for nonmetropolitan patients with PM.

© 2025 The Author(s). Cancer Medicine published by John Wiley & Sons Ltd.

In plain English

This was a retrospective study of US cancer registry data (SEER 18 registries, covering about 34% of the US population). It compared pleural mesothelioma in metropolitan and nonmetropolitan counties. It included 8519 patients aged 20 or older diagnosed from 2004 to 2021: 7607 metropolitan and 912 nonmetropolitan. The study did not measure asbestos exposure. Average age-adjusted incidence was 1.1 per 100,000 in metropolitan areas and 0.9 in nonmetropolitan areas. Metropolitan incidence fell to 0.8 by 2021. Nonmetropolitan incidence stayed at 0.9 until 2017, then fell to 0.5 in 2021. Stage at diagnosis did not differ significantly between the groups. Nonmetropolitan patients less often received chemotherapy (44.8% versus 48.6%) and surgery (20.2% versus 24.4%). By 2020, one-year cancer-specific survival was 50.3% in metropolitan areas and 27.7% in nonmetropolitan areas. After adjustment for other factors, nonmetropolitan residence was associated with a higher hazard of death from the cancer (HR 1.18, 95% CI 1.09 to 1.27). The authors concluded that the survival gap had narrowed but a difference remained. They noted that the database does not record immunotherapy.

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 registry study (SEER 18), with incidence trend (joinpoint) analysis, propensity score matching, Kaplan–Meier and Cox proportional hazards survival analysis
• Who was studied: 8519 patients aged 20 or older with microscopically confirmed pleural mesothelioma diagnosed 2004–2021 in the US SEER 18 registries: 7607 (89.3%) in metropolitan and 912 (10.7%) in nonmetropolitan areas
• Exposure: The comparison was place of residence (metropolitan versus nonmetropolitan county). Asbestos exposure and fiber type were not measured in this study.
• Main results:
  • Over 2004–2021, average age-adjusted incidence was 1.1 per 100,000 in metropolitan areas and 0.9 in nonmetropolitan areas (incidence rate ratio 0.85, p less than 0.001)
  • Metropolitan incidence declined from 2014 to 0.8 in 2021, at -4.9% per year (95% CI -8.1%, -3.9%)
  • Nonmetropolitan incidence was stable at 0.9 from 2004 to 2017, then declined to 0.5 in 2021, at -16.2% per year (95% CI -40.4%, -6.0%)
  • Nonmetropolitan patients were more often non-Hispanic White (88.9% versus 77.2% of metropolitan patients)
  • Nonmetropolitan patients were less likely to receive chemotherapy (44.8% versus 48.6% of metropolitan patients) and surgery (20.2% versus 24.4%)
  • No significant differences between the groups in age at diagnosis, histologic subtype, stage at diagnosis, or receipt of radiation
  • By 2020, one-year cancer-specific survival was 50.3% in metropolitan areas and 27.7% in nonmetropolitan areas
  • For 2016, the last year five-year survival could be examined, five-year cancer-specific survival was 10.7% in metropolitan areas and 6.4% in nonmetropolitan areas
  • In propensity-matched cohorts of 912 patients each, one-year cancer-specific survival was 44.4% in the metropolitan cohort and 34.3% in the nonmetropolitan cohort
  • In multivariate Cox analysis, nonmetropolitan residence was associated with a higher hazard of death (HR 1.18, 95% CI 1.09–1.27, p less than 0.001)
  • Not receiving chemotherapy (HR 1.38, 95% CI 1.31–1.50) or surgery (HR 1.41, 95% CI 1.33–1.50) was also associated with higher hazard of death
• The authors' conclusion: The authors concluded that incidence fell and survival improved in both areas, but a survival difference between metropolitan and nonmetropolitan areas remained. In their view, more must be done to reduce these disparities.
• Limitations the authors state:
  • Detailed patient-level data such as lab values or pathology results were not available
  • The database does not record whether patients received immunotherapy, now a recommended first-line treatment
  • The database uses a 'fibrous mesothelioma' subtype that is not used in clinical practice but is synonymous with sarcomatoid mesothelioma

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Epidemiology, SEER, Incidence, Chemotherapy, Multivariate Analysis.

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• Response to Letter to the Editor Regarding "Ambient Asbestos Fiber Concentrations and Long-Term Trends in Pleural Mesothelioma Incidence Between Urban and Rural Areas in the United States (1973-2012)" by Finkelstein — K.A. Keeton, M.E. Glynn, et al. (2018)
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