The Association Of Silicosis And Carcinoma Of The Lung

Our plain-English summary of The Association Of Silicosis And Carcinoma Of The Lung, by M.O. Klotz (1939).

The study

• Author: M.O. Klotz
• Published: American Journal Of Cancer 35:38-49 (1939)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 003181. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article concerns silica, not asbestos. Asbestosis appears only in the author's review of others' reports. The author reviewed earlier literature, then examined 50 cases of silicosis seen by the University of Toronto Department of Pathology and Bacteriology from 1925 to 1936. These were compared with 4,500 Toronto General Hospital autopsies from the same years. Among the 50 silicosis cases, 9 had cancer of any organ (18 per cent), which the author said was not significantly different from the 17.7 per cent in the unselected autopsies. Four of the 50 (8 per cent) had primary bronchogenic lung cancer, compared with 53 of 4,500 (1.17 per cent) unselected autopsies. The four men, average age 48, had worked in mines or a granite quarry, and none was diagnosed by X-ray. The author concluded that the coexistence of lung cancer and silicosis appeared not to be purely accidental. The author also said confirmation required more accurate statistical data, noted that comparing a selected group of 50 with 4,500 was not entirely accurate, and called the part played by silica obscure.

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: Review of a pathology department's silicosis cases compared with general hospital autopsies, with four detailed case reports and a brief literature review
• Who was studied: 50 cases of silicosis examined by the Department of Pathology and Bacteriology, University of Toronto, 1925 to 1936. Twenty-five came from the department's autopsy files and 25 were submitted by the Department of Health of Ontario. The comparison group was 4,500 autopsies on patients dying in the Toronto General Hospital over the same years.
• Exposure: Silica dust, in the form of silicosis. The four lung cancer cases had worked in the nickel mines of Sudbury and a granite quarry, in English tin mines, and in Northern Ontario gold mines, with exposure ranging from more than 5 years to 30 years. No asbestos exposure was studied.
• Main results:
  • Among the 50 silicosis cases, 4 had primary bronchogenic (lung) cancer, which was 8 per cent of the silicosis cases. These 4 made up 45 per cent of the 9 cancers found in this group.
  • Among the 4,500 unselected autopsies, 53 had primary bronchogenic cancer, which was 1.17 per cent of all autopsies and 6.5 per cent of cancers.
  • Cancer of any organ was found in 9 of the 50 silicosis cases (18 per cent). The author said this was not significantly different from the unselected autopsies, where 808 cancers (17.7 per cent) were found.
  • In none of the four lung cancer cases with silicosis could the tumour be diagnosed by X-ray, even in retrospect.
  • The four patients with silicosis and lung cancer had an average age of 48. All except Case 1 had been exposed to silica for more than twenty years.
  • Case 1 showed the most advanced fibrosis and the highest silica percentage (33.98 per cent). The other three cases showed only minimal or slight fibrosis attributable to silica.
  • All four tumours were at the hilum. Cases 1, 2 and 3 were spindle-cell or oat-cell anaplastic tumours, and Case 4 showed poor differentiation towards the epidermoid type.
  • Except in Case 1, no anatomical relationship could be shown between the tumour and the silicotic fibrosis.
• The authors' conclusion: The author concluded that the department's figures and the literature suggest the coexistence of lung cancer and silicosis is not purely accidental. In the author's view, people with silicosis, even in its early stages, may be more prone to lung cancer than people not so exposed. The author added that complete confirmation requires further accurate statistical data.
• Limitations the authors state:
  • The author said comparing a selected group of 50 cases with a control group of 4,500 is not entirely accurate.
  • The 18 per cent cancer figure for the silicosis group may be too low. Much of the Department of Health material consisted of the chest organs only, so cancers elsewhere in the body could not be found.
  • The hospital comparison population was largely urban and was not a true cross-section of the population.
  • Because only limited material was available, spread of the tumours to distant organs could not be determined in some cases.
  • The author said the part actually played by silica is obscure.

Topics

Medical terms in this study, explained in our Lexicon: Silicosis, Carcinoma, Pathology, Bronchogenic Carcinoma, Lung Cancer.

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