Incidence of malignant mesothelioma of the pleura in Québec and Canada from 1984 to 2007, and projections from 2008 to 2032

Our plain-English summary of Incidence of malignant mesothelioma of the pleura in Québec and Canada from 1984 to 2007, and projections from 2008 to 2032, by A. Krupoves, M. Camus, L. De Guire (American Journal of Industrial Medicine, 2015).

The study

• Authors: A. Krupoves, M. Camus, L. De Guire
• Journal: American Journal of Industrial Medicine
• Published: 2015;58(5):473-82
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Continuous increase in male incidence of malignant mesothelioma of the pleura (MMP) despite the drop of asbestos production since 1980 in Québec motivated this study aiming to assess when the rates of MMP will decline.

Methods: Age-standardized rates and trends were estimated over the 1984-2007 period by sex for Québec versus "Canada-excluding-Québec" (Can-Qc). An age-cohort regression was used to make projections for 2008-2032.

Results: Average rates of MMP in Québec men and women were significantly higher than in Can-Qc. Projected rates peak between 2003 and 2012 in all four study populations and decline thereafter.

Conclusion: The higher MMP rates and observed/projected time patterns in Québec men are consistent with past asbestos production and occupational exposures. The excess in Québec women may also be explained by domestic and, for some, by neighborhood exposures. To pursue the decrease in MMP rates beyond 2032, efforts to reduce asbestos exposure should be maintained.

© 2015 Wiley Periodicals, Inc.

In plain English

This study used Canadian Cancer Registry data to describe how often malignant mesothelioma of the pleura (MMP) was diagnosed from 1984 to 2007 in Quebec and in the rest of Canada. It then used an age-cohort statistical model to project rates for 2008 to 2032. Quebec had 1,607 male and 404 female cases, and the rest of Canada had 3,484 male and 584 female cases. The average rate in Quebec men was 2.12 per 100,000 person-years, 1.45 times (95% CI 1.37-1.54) the rate in other Canadian men. In Quebec women it was 0.42 per 100,000 person-years, 2.0 times (95% CI 1.76-2.27) the rate in other Canadian women. Rates in Quebec men rose 2.71% per year on average, with a significant slowdown after 1996. Projected rates peaked between 2003 and 2012 and then declined. The authors concluded that the higher rates in Quebec men are consistent with past asbestos production and occupational exposures. They cautioned that projections for women are uncertain.

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 registry study of incidence rates and time trends, with an age-cohort Poisson regression model used to project future rates
• Who was studied: New cases of malignant mesothelioma of the pleura recorded by the Canadian Cancer Registry, 1984–2007, in four groups: men and women in Quebec (1,607 male and 404 female cases) and men and women in Canada excluding Quebec (3,484 male and 584 female cases)
• Exposure: The study did not measure individual asbestos exposure. It compared observed and projected rates with yearly Canadian asbestos fiber production, and reported a lag of about 35 to 40 years.
• Main results:
  • Men: the average MMP incidence in Quebec was 2.12 per 100,000 person-years, 1.45 times (95% CI 1.37-1.54) the rate of 1.46 per 100,000 person-years in men in Canada excluding Quebec
  • Women: the average MMP incidence in Quebec was 0.42 per 100,000 person-years, 2.0 times (95% CI 1.76-2.27) the rate of 0.21 per 100,000 person-years in women in Canada excluding Quebec
  • Quebec men: age-adjusted incidence rose significantly by 2.71% per year on average over 1984–2007. The rise was 6.41% per year before 1996 and a non-significant 0.65% per year in 1996–2007, a significant slowdown between the two periods.
  • Men in Canada excluding Quebec: incidence rose significantly by 2.00% per year on average over 1984–2007. The rise was 3.06% per year before 1996 and a non-significant 0.33% per year in 1996–2007, also a significant slowdown.
  • Quebec women: incidence rose significantly by 2.60% per year over 1984–2007. Neither the separate period trends nor the slowdown were statistically significant. Women in Canada excluding Quebec: incidence rose significantly by 2.53% per year over 1984–2007, and neither period trend was statistically significant.
  • Quebec men, by birth cohort: age-specific risk increased 6.2-fold between the 1900–1904 and 1940–1944 birth cohorts, then declined 13.6-fold between the 1940–1944 and 1960–1964 cohorts
  • Projections for men: age-adjusted rates should have peaked at about 2.74 per 100,000 person-years in 2008–2012 in Quebec, and at about 1.73 in 2003–2012 in Canada excluding Quebec. By 2032 rates should fall below 1.50 in Quebec men and below 1.00 in men in Canada excluding Quebec.
  • Projections for women: Quebec women should have peaked at about 0.51 per 100,000 person-years in 2008–2012, falling to pre-1990 levels by 2032. Women in Canada excluding Quebec should have peaked at about 0.30 around 2008–2012, falling to about 0.26 in 2028–2032.
  • Projected case numbers in Quebec: a peak of about 150 male cases per year around 2020 and 35 female cases per year around 2025, averaging 180 cases per year for both sexes over 2008–2032. Rest of Canada: about 265 male cases per year around 2020 and 59 female cases per year around 2030, averaging 315 per year.
  • Later data for Quebec men in 2008–2010 showed an average age-adjusted rate of 2.1 per 100,000 person-years, below the 2.74 predicted for 2008–2012. The authors said more data are needed to test the predictions.
• The authors' conclusion: The authors concluded that the higher MMP rates and the observed and projected time patterns in Quebec men are consistent with past asbestos production and occupational exposures. They wrote that the excess in Quebec women may also be explained by domestic and, for some, neighborhood exposures, and that the projections suggest a downturn in rates starting between 2003 and 2012. They called for sustained efforts to keep asbestos exposures as low as possible and for continued surveillance.
• Limitations the authors state:
  • Projections for women are statistically uncertain because several age-cohort categories had very few or no cases
  • Excluding cases under 40 years of age may have underestimated projected rates, although the authors said this effect would be small
  • New immunohistochemical testing introduced in the 1990s may have somewhat distorted trends and projections, although no statistically significant period effect was found
  • False positive and false negative diagnosis rates for MMP were cited as roughly similar, at 10-20%
  • The authors could not explain with certainty the excess in Quebec women and lacked historical evidence for the household-exposure explanation. Data on past exposure in construction and manufacturing were too scarce.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleura, Occupational Exposure, Environmental Exposure, Asbestos Exposure.

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