Epidemiology of primary malignant mesothelial tumors in Canada

Our plain-English summary of Epidemiology of primary malignant mesothelial tumors in Canada, by A.D. McDonald, A. Harper, J.C. McDonald, et al (Cancer, 1970).

The study

• Authors: A.D. McDonald, A. Harper, J.C. McDonald, O.A. el-Attar
• Journal: Cancer
• Published: 1970;26(4):914-9
• Cited by: 127 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M nos. 001400, 001401).

In plain English

This national case-control survey studied fatal primary malignant mesothelial tumors in Canada. The authors contacted pathologists and registered 165 cases from 1959 to mid-1968: 113 pleural, 45 peritoneal, 3 pleural and peritoneal, and 4 pericardial. Each case was matched to a secondary lung cancer death and, in all but 2 instances, to a primary lung cancer death. Interviewers unaware of each person's group questioned relatives and friends about jobs, residence, household dust and smoking. Questionnaires were completed for 447 (91%) of 493 cases and controls. Average yearly incidence in 1960-1967 was 1.0 per million. Among men, 20% of mesothelial tumor cases had definite or probable occupational asbestos exposure. That was a substantial excess over both control groups (P less than 0.001). The excess came mostly from asbestos textile manufacture, brake lining installation and insulation work, with little from mining or milling. Mesothelial tumor cases and secondary lung cancer controls had almost identical smoking habits. The authors concluded this suggests either that chrysotile is less associated with these tumors than other forms of asbestos, or that something in addition to asbestos is necessary.

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: National case registry with a case-control comparison using two matched control series (secondary lung cancer and primary lung cancer). Histories were collected and coded blind from relatives and friends.
• Who was studied: All fatal primary malignant mesothelial tumors known to pathologists in Canada between 1959 and mid-1968: 165 cases (108 male, 57 female; 113 pleural, 45 peritoneal, 3 pleural and peritoneal, 4 pericardial). Each was matched for sex, and as closely as possible for age and date of death, to one secondary lung cancer death. Each was also matched to one primary lung cancer death, except in 2 instances where no adequately matching primary lung cancer case could be found (Table 3 lists 163 primary lung cancer controls). Questionnaires were completed for 447 (91%) of 493 cases and controls.
• Exposure: Occupational exposure to asbestos, classified as definite, probable, possible or unlikely, and to cement, copper, fiber glass, nickel, rubber and wood. The study also covered residence near asbestos mines, household (domestic) exposure from family members' dusty clothes, and cigarette smoking.
• Main results:
  • Average annual incidence in 1960-1967 was 1.0 per million population. It was higher in Quebec (1.5) than in Ontario (0.8) or the rest of Canada (0.9).
  • Among cases, males predominated by 2.4 to 1.
  • Men with mesothelial tumors had a substantial excess of definite or probable occupational asbestos exposure compared with both control groups (P less than .001). In 60% of cases, occupational exposure was considered unlikely.
  • Most of the excess came from men in asbestos textile manufacture, brake lining installation, or insulation work. Mine or mill workers contributed little (3 mesothelial tumor cases, 1 secondary and 1 primary lung cancer control). Table 6 lists 21 definite or probable occupations in the mesothelial tumor group, 3 in the secondary lung cancer group and 4 in the primary lung cancer group.
  • For the 21 cases with definite or probable exposure, the time from first exposure to death ranged from 16 to 50 years.
  • No association was found with possible (lesser) occupational exposure or with residence in asbestos-mining areas.
  • At least possible domestic contact with asbestos dust was found in 10% of mesothelial tumor cases, compared with 5% of the secondary lung cancer group.
  • Smoking habits of mesothelial tumor cases and secondary lung cancer controls were almost identical. The primary lung cancer group had smoked considerably more.
  • Nine men with mesothelial tumors had worked in jobs unrelated to asbestos but involving copper, nickel, rubber or fiber glass, compared with one in each control group. The authors called the interpretation of this doubtful.
• The authors' conclusion: The authors concluded that these tumors are rare in Canada and that an association with definite or probable occupational asbestos exposure was clearly demonstrated. Because almost all of the excess was in manufacture and industrial application rather than mining or milling, they suggested that either chrysotile is less associated with mesothelial tumors than other forms of asbestos, or that something in addition to asbestos is necessary. If there is such an additional factor, they wrote, it is not cigarette smoking.
• Limitations the authors state:
  • More cases were found in 1966 and 1967, possibly because of recent interest and poorer hospital records for earlier years, so the true rate of increase is difficult to assess.
  • Diagnoses had not yet been reviewed by a panel of pathologists.
  • The case series may have been diluted by cases that other investigators would not have accepted.
  • The primary lung cancer series was selected to match the mesothelial cases, so it cannot be considered representative in itself.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Epidemiology.

Related studies

• Primary tumors and cysts of the heart and pericardium — H.A. McAllister (1979)
• Epidemiologic surveillance of mesothelioma in Canada — A.D. McDonald, J.C. McDonald (1973)
• Surgical pathology of primary cardiac and pericardial tumors — C. Basso, M. Valente, et al. (1997)
• Epidemiology of mesothelioma in Israel — C. Lemesch, R. Steinitz, et al. (1976)
• Epidemiology of mesothelial tumors in the London area — M.L. Newhouse, H. Thompson (1965)
• Cardiac masses: assessment by MR imaging — J.T. Lund, R.L. Ehman, et al. (1989)

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