Malignant pleural mesothelioma: a population-based study of survival

Our plain-English summary of Malignant pleural mesothelioma: a population-based study of survival, by M.T. Milano, H. Zhang (Journal of Thoracic Oncology, 2010).

The study

• Authors: M.T. Milano, H. Zhang
• Journal: Journal of Thoracic Oncology
• Published: 2010;5(11):1841-8
• Cited by: 145 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: This study characterizes the overall survival (OS) and variables affecting OS in patients with malignant pleural mesothelioma.

Methods: A total of 9701 patients with malignant pleural mesothelioma, diagnosed from 1973 to 2006, were retrospectively analyzed using the population-based surveillance, epidemiology, and end results database.

Results: The 6-month, 1-year, and 5-year OS were 55, 33, and 5%, respectively. Significantly adverse prognostic factors from univariate analyses included older age, male gender, higher tumor grade, nonepithelioid histology, higher stage, no cancer-directed surgery, and no radiotherapy. Race was not significant. Patients undergoing cancer-directed surgery and radiotherapy, when grouped by stage, histology, or grade, had the best median survival (versus radiotherapy or surgery alone or no surgery/radiotherapy). From Cox proportional hazards analyses, grade (range, 1-4) was associated with a hazard ratio (HR) of >1.5 (p < 0.0001), and not undergoing cancer-directed surgery was associated with a HR of >1.4 (p < 0.0001). Male gender and older age were also significantly adverse factors. Tumor histology (HR = 1.5) and nonlocalized stage (HR = 1.3) were significant in a Cox model omitting tumor grade. With grade and histology included in the Cox model, the HRs of histology and stage were of smaller magnitude and not significant.

Conclusions: From a population-based registry analysis of patients with malignant pleural mesothelioma, tumor grade and cancer-directed surgery seem to have the greatest impact on OS. Although being amenable to surgery likely reflects more indolent disease and/or better performance status and cardiopulmonary function, the significantly favorable impact of surgery, accounting for tumor grade, histology, and stage, may reflect a therapeutic benefit.

In plain English

This retrospective study used United States SEER cancer registry records for 9701 patients with malignant pleural mesothelioma diagnosed from 1973 to 2006. It examined how long patients survived and which factors were linked to survival. Asbestos exposure was not examined, and the authors listed this as a weakness. Estimated overall survival was 55% at 6 months, 33% at 1 year and 5% at 5 years. In unadjusted comparisons, older age, male gender, higher tumor grade, non-epithelioid tumor type, more advanced stage, and not having cancer-directed surgery or radiation were linked to shorter survival. Race was not. In adjusted analyses, each step up in tumor grade carried a hazard ratio of about 1.5, and having surgery was linked to a lower risk of death (hazard ratios 0.6 to 0.7). The authors concluded that grade, histology and surgery seemed to matter most. They said the surgery finding may reflect a therapeutic benefit, but likely also reflects fitter patients with slower-growing disease being chosen for surgery. Tumor grade was missing for 90% of patients.

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, descriptive analysis of a population-based cancer registry (SEER)
• Who was studied: 9701 patients with malignant pleural mesothelioma diagnosed from 1973 to 2006 in the US SEER 17 registries. This includes 9392 coded as pleura and 309 coded as lung and bronchus, grouped together as pleural mesothelioma. Median age was 72 and 81% were male. Autopsy-only, death-certificate-only and benign cases were excluded.
• Exposure: Asbestos exposure was not studied. The registry data could not account for exposure to tobacco or asbestos. The factors analyzed were age, race, gender, year of diagnosis, tumor grade, histology, stage, cancer-directed surgery and radiation.
• Main results:
  • Among all patients with malignant pleural mesothelioma, overall survival was 55% at 6 months, 33% at 1 year and 5% at 5 years.
  • In univariate analyses, the adverse prognostic factors were older age, male gender, higher grade, nonepithelioid histology, higher stage, no cancer-directed surgery and no radiation therapy. Race was not significant for any stage group.
  • In Cox models, older age was a significantly adverse factor in every model, with a hazard ratio of 1.02 per year.
  • Higher tumor grade had a hazard ratio of 1.585 (confidence interval 1.465–1.715) in the model omitting histology (903 patients). It had a hazard ratio of 1.548 (1.364–1.756) in the model including all variables (361 patients). Both were p 0.0001.
  • Nonepithelioid histology had a hazard ratio of 1.511 (1.388–1.645) when grade was left out of the model (2907 patients). When grade was included (361 patients), the hazard ratio was 1.148 (0.861–1.532) and was not significant (p 0.35).
  • Cancer-directed surgery was a significantly favorable factor in all Cox models. The hazard ratio was 0.664 (0.627–0.704) in the 8128-patient model and 0.615 (0.476–0.794) in the 361-patient model with all variables.
  • Male gender was significantly adverse in the largest model, with a hazard ratio of 1.232 (1.161–1.307). It was not significant in the model omitting histology (1.100, 0.933–1.298).
  • Median survival after both surgery and radiation was 58.0, 13.0, 11.5 and 6.3 months for grades 1 to 4. For patients with neither treatment it was 16.8, 10.8, 3.3 and 2.8 months.
• The authors' conclusion: The authors described the analysis as hypothesis generating. They concluded that tumor grade, histology and cancer-directed surgery seemed to have the greatest impact on overall survival. Because histology lost significance once grade was included, they suggested grade may be more prognostic. They said the favorable association with surgery likely reflects more indolent disease and better fitness, but may also reflect a therapeutic benefit.
• Limitations the authors state:
  • The study was retrospective. It could not account for performance status, weight loss, blood abnormalities, LDH levels, presenting symptoms, or tobacco and asbestos exposure.
  • Grade and histology were missing for most patients. Grade was unavailable in 90% of patients.
  • Tumor pathology could not be reviewed with modern immunohistochemistry to verify the diagnosis.
  • The data could not show whether treatment was curative or palliative in intent.
  • Chemotherapy use, chemotherapy agents, radiation dose and radiation fields were unknown.
  • Factors used to select patients for surgery were not accounted for and likely contribute to the survival advantage seen with surgery.
  • Many specialized centers do not report to SEER, so outcomes at those centers may not be reflected.

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, Overall Survival, Epidemiology, Histology, Median Survival, Hazard Ratio, Performance Status.

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