Malignant mesothelioma incidence by nation-wide cancer registry: a population-based study

Our plain-English summary of Malignant mesothelioma incidence by nation-wide cancer registry: a population-based study, by K. Tomasson, G. Gudmundsson, H. Briem, et al (Journal of Occupational Medicine and Toxicology, 2016).

The study

• Authors: K. Tomasson, G. Gudmundsson, H. Briem, V. Rafnsson
• Journal: Journal of Occupational Medicine and Toxicology
• Published: 2016;11:37
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant mesothelioma caused by asbestos exposure has a long latency period. A ban on asbestos use may not be apparent in decreased incidence in the population until after several decades. The aim was to evaluate changes in the incidence of malignant mesothelioma, and the possible impact of the asbestos ban implemented in Iceland in 1983.

Methods: This is a population study on aggregate level; the source of data was the Icelandic Cancer Registry, the National Cause-of-Death Registry, and the National Register. Volume of asbestos import was obtained from Customs Tariff. The import figures reflect fairly accurately the amount used, as there are no mines in the country.

Results: Asbestos import peaked in 1980 at 15.0 kg/capita/year, diminishing to 0.3 kg/capita/year ten years after the ban in 1983, and to zero in the most recent years. Seventy-nine per cent of the cases of malignant mesothelioma were men, and 72 % were of pleural origin. Mesothelioma incidence increased steadily from 1965 to 2014, when it reached 21.4 per million among men, and 5.6 among women. Mortality in 2014 was 22.2 per million among men, and 4.8 among women.

Conclusion: Malignant mesothelioma incidence and mortality increased in the population during the period, despite the ban on asbestos use from 1983. This is in agreement with the long latency time for malignant mesothelioma. In line with the previously high per capita volume of asbestos import, many buildings, equipment, and structures contain asbestos, so there is an on-going risk of asbestos exposure during maintenance, renovations and replacements. It is thus difficult to predict when the incidence of malignant mesothelioma will decrease in the future. During the last ten-year period, the incidence in Iceland was higher than the recently reported incidence in neighbouring countries.

In plain English

This population-based study counted malignant mesothelioma cases in Iceland's nation-wide cancer registry from 1965 to 2014 and deaths in the national cause-of-death registry from 1996 to 2014. Customs records showed asbestos imports peaked in 1980 at 3500 tons (15.0 kg per person per year); the types of asbestos were not recorded. A ban with certain exceptions began in 1983. There were 60 cases in men and 16 in women. Among men, the yearly rate per million men aged 15 or older rose from 1.4 in 1965–1974 to 21.4 in 2005–2014, a statistically significant trend. Among women aged 15 or older, rates stayed low (5.6 per million in 2005–2014) and the trend was not statistically significant. In men, 97% of cases were pleural; in women, 56% were pleural and 44% peritoneal. Mortality showed no obvious increase over the short period available. The authors concluded that incidence seems to be increasing despite the ban. They noted that cases were not re-checked by an expert pathologist and that the registry does not routinely collect exposure information.

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 observational study using national registries at aggregate level
• Who was studied: All malignant mesothelioma cases in the nation-wide Icelandic Cancer Registry, 1965–2014: 60 men and 16 women. Deaths came from the National Cause-of-Death Registry, 1996–2014. Rates were calculated using Iceland's population aged 15 years or older.
• Exposure: Annual import of asbestos and asbestos-containing goods into Iceland, from customs records, 1976–2014. The types of asbestos were not indicated. No individual occupational or environmental exposure data were collected.
• Main results:
  • Asbestos imports peaked in 1980 at 3500 tons, given as 1500 tons per 100,000 inhabitants or 15.0 kg per person per year. The authors linked this to construction of district heating systems using asbestos cement pipes.
  • A ban on asbestos use, with certain exceptions, was implemented in 1983. Imports fell that year, then rose again over five years and peaked a second time in 1992 at 800 tons.
  • Men: the annual incidence per million men aged 15 or older rose steadily across ten-year periods. It went from 1.4 (95% CI 0.1–7.1; 1 case) in 1965–1974 to 21.4 (95% CI 14.4–30.7; 27 cases) in 2005–2014.
  • Men: compared with 1965–1974, the relative risk in 2005–2014 was 14.90 (95% CI 2.03–109.7), and the trend was statistically significant.
  • Women: rates were low and changes were not straightforward. Annual incidence per million women aged 15 or older was 2.9 in 1965–1974 and 5.6 (95% CI 2.4–11.0) in 2005–2014. There were no cases in 1975–1984.
  • Women: the relative risk for 2005–2014 versus 1965–1974 was 1.92 (95% CI 0.40–9.22). The trend was not statistically significant (p-value 0.11).
  • Location: among men, 97% of cases were pleural (58 of 60). Among women, 56% were pleural and 44% peritoneal (9 and 7 of 16).
  • Mortality: among men, 14.4 per million in 1996–2004 and 22.2 per million in 2005–2014 (RR 1.54, 95% CI 0.82–3.00). Among women, 4.1 and 4.8 per million (RR 1.17, 95% CI 0.32–4.69). The authors noted no obvious increase over this short period, though the rates and RR were high.
• The authors' conclusion: The authors concluded that malignant mesothelioma incidence seems to be increasing in Iceland. They took this to indicate no reduction yet in the influence of previous asbestos exposure, despite the ban first implemented in 1983. They added that incidence in the last ten-year period was higher than recently reported in neighbouring Scandinavian countries.
• Limitations the authors state:
  • Cases were not histologically reviewed by an expert pathologist for this study. The relatively high proportion of peritoneal cases among women may raise concern of diagnostic error.
  • Data come from one country only, which may limit how far the results apply elsewhere.
  • The cancer registry does not routinely collect information on occupational or environmental exposure, or on survival.
  • The rise in incidence may partly reflect better diagnosis and greater watchfulness for the cancer.
  • Counts of incident cases and of deaths did not agree, partly because of the lag between diagnosis and death.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Cancer Registry, Asbestos Exposure, Latency.

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