Incidence, mortality and survival in malignant pleural mesothelioma before and after asbestos in Denmark, Finland, Norway and Sweden

Our plain-English summary of Incidence, mortality and survival in malignant pleural mesothelioma before and after asbestos in Denmark, Finland, Norway and Sweden, by K. Hemminki, A. Försti, T. Chen, et al (BMC Cancer, 2021).

The study

• Authors: K. Hemminki, A. Försti, T. Chen, A. Hemminki
• Journal: BMC Cancer
• Published: 2021;21(1):1189
• Type of article: Historical article
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant pleural mesothelioma (MPM) is a rare but fatal cancer, which is largely caused by exposure to asbestos. Reliable information about the incidence of MPM prior the influence of asbestos is lacking. The nationwide regional incidence trends for MPM remain poorly characterized. We use nationwide MPM data for Denmark (DK), Finland (FI), Norway (NO) and Sweden (SE) to assess incidence, mortality and survival trends for MPM in these countries.

Methods: We use the NORDCAN database for the analyses: incidence data were available from 1943 in DK, 1953 in FI and NO and 1958 in SE, through 2016. Survival data were available from 1967 through 2016. World standard population was used in age standardization.

Results: The lowest incidence that we recorded for MPM was 0.02/100,000 for NO women and 0.05/100,000 for FI men in 1953-57, marking the incidence before the influence of asbestos. The highest rate of 1.9/100,000 was recorded for DK in 1997. Female incidence was much lower than male incidence. In each country, the male incidence trend for MPM culminated, first in SE around 1990. The regional incidence trends matched with earlier asbestos-related industrial activity, shipbuilding in FI and SE, cement manufacturing and shipbuilding in DK and seafaring in NO. Relative 1-year survival increased from about 20 to 50% but 5-year survival remained at or below 10%.

Conclusion: In the Nordic countries, the male incidence trends for MPM climaxed and started to decrease, indicating that the prevention of exposure was beneficial. Survival in MPM has improved for both sexes but long-term survival remains dismal.

© 2021. The Author(s).

In plain English

This ecological study used NORDCAN cancer registry data to follow malignant pleural mesothelioma in Denmark, Finland, Norway and Sweden from registration's start (1943 to 1958) through 2016. The lowest age-standardized rate was 0.02 per 100,000, for Norwegian women in 1953–57; Finnish men started at 0.05. Male rates peaked at 1.9 per 100,000 in Denmark (around 1997), 1.7 in Norway (2003), 1.5 in Finland (2006) and 1.25 in Sweden (early 1990s). Norwegian and Swedish male rates then fell by roughly a third; female rates were much lower. Among men, regional rates within countries differed up to about 3-fold, peaking at 3.2 per 100,000 in north Jutland, Denmark, in 2006. In pooled data for all Nordic men, age-specific incidence rose across birth cohorts until the 1937/1947 cohorts, then leveled off and declined. Relative 1-year survival rose from about 20% to 50%; 5-year survival stayed at or below 10%. The authors concluded that falling male incidence and improved survival suggest alleviation of the problem. They named the ecological design and the disease's rarity, which caused large data fluctuations, as the main limitation.

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: Registry-based ecological study of time trends in incidence, mortality and relative survival
• Who was studied: Malignant pleural mesothelioma cases recorded in the national cancer registries of Denmark, Finland, Norway and Sweden (NORDCAN). Incidence data ran from 1943 (Denmark), 1953 (Finland, Norway) and 1958 (Sweden) through 2016, and survival data from 1967. Male case numbers ranged from 2065 (Finland) to 3801 (Sweden); female case numbers ranged from 357 (Norway) to 1046 (Denmark).
• Exposure: Individual asbestos exposure was not measured. The authors interpreted national and regional incidence trends against asbestos consumption figures and asbestos-related industries taken from other sources (cement manufacturing, shipbuilding, seafaring). Fiber types were not analyzed.
• Main results:
  • Lowest recorded incidence: 0.02/100,000 for Norwegian women in 1953–57, compared with 0.05/100,000 for Finnish men
  • Danish men: incidence started at 0.3/100,000 in 1943–47 and peaked at 1.9/100,000 around 1997
  • Finnish men: incidence started at 0.05/100,000 in 1953–57 and reached a maximum of 1.5/100,000 in 2006
  • Norwegian men: incidence started at 0.1/100,000 and peaked at 1.7/100,000 in 2003; by 2012–16 it had dropped almost by a third
  • Swedish men: broad maximum of 1.25/100,000 in the early 1990s, then a drop by a third
  • Incidence was far lower in women than in men. Danish women peaked at 0.45/100,000 in 1976, Finnish women at 0.38/100,000 in 1989, and Norwegian and Swedish women's rates fluctuated around 0.2/100,000.
  • Regional differences in men: in north Jutland (Denmark), incidence peaked at 3.2/100,000 in 2006
  • Regional differences in men: the north Jutland peak was almost 3-fold the lowest concurrent regional rate in Denmark
  • Regional differences in men: in the Turku region (Finland), incidence reached 2.3/100,000 in 2005
  • Combined Nordic male dataset (all four countries pooled): age-specific incidence increased across birth cohorts from 1877 onwards until the 1937/1947 cohorts, then leveled off and turned into decline
  • Relative 1-year survival for men was around 20% in 1967–71
  • Relative 1-year survival for women was initially 20–30%; the latest survival, about 50%, was at the male level
  • Relative 5-year survival was at or below 10% in the latest period for both sexes
  • In Finland, mortality followed the incidence curve
• The authors' conclusion: The authors concluded that in the Nordic countries the male incidence trends have turned down and survival has improved for men and women, which suggests alleviation of the problem. They also stated that they cannot predict when, or if, asbestos-related MPM will end there.
• Limitations the authors state:
  • The main limitation is the ecological nature of the study together with the rarity of MPM, which caused large fluctuations in data points; the authors state the data only allow speculation about the trends
  • Because MPM is rare, the data points fluctuate widely
  • Results depend on MPM having been reliably diagnosed; a new cancer type may be overlooked before diagnostic criteria are set
  • Danish and Norwegian incidence and mortality curves showed gaps at times, for unknown reasons
  • Swedish MPM-specific mortality data were available only from 1998 and were not shown

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.

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• Incidence trends of mesothelioma in Norway, 1965-1999 — B. Ulvestad, K. Kjaerheim, et al. (2003)
• Retrospective exposure assessment for carcinogenic agents in bitumen waterproofing industry in Finland and denmark — P. Anttila, P. Heikkilä, et al. (2009)
• Mesothelioma incidence seems to have leveled off in Sweden — K. Hemminki, X. Li (2003)
• Incidence of lung cancer by histological type among asbestos cement workers in Denmark — E. Raffn, E. Lynge, et al. (1993)

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