Lung cancer in the lower lobe is associated with pulmonary asbestos fiber count and fiber size

Our plain-English summary of Lung cancer in the lower lobe is associated with pulmonary asbestos fiber count and fiber size, by S. Anttila, A. Karjalainen, O. Taikina-aho, et al (Environmental Health Perspectives, 1993).

The study

• Authors: S. Anttila, A. Karjalainen, O. Taikina-aho, P. Kyyrönen, H. Vainio
• Journal: Environmental Health Perspectives
• Published: 1993;101(2):166-70
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

We studied exposure to asbestos, pulmonary fibrosis, fiber count, and fiber size in relation to the lobar origin of lung cancer in 90 consecutive patients. Among the 32 patients with a history of occupational exposure to asbestos, 22 were construction workers. The proportion of lower-lobe tumors increased with the duration of exposure from 45% in those working less than 15 years to 82% in those working 15 years or more in the construction trade, as compared with 25% in patients who were probably not exposed. The location of the tumor in the lower lobe was explained by the high number of total fibers [odds ratio (OR) = 9.0, CI = 2.3-34.6), of fibers 3 microns and longer (OR = 22.1, CI = 3.9-125), and fibers of anthophyllite (OR = 14.6, CI = 2.4-83.4) and crocidolite (OR = 7.0, CI = 1.2-41.2) when the effect of smoking and fibrosis was adjusted in the logistic regression analysis. The location of the tumor did not correlate with fibrosis, pack-years smoked, or the number of short (< 3 microns) fibers. Our findings suggest that asbestos causes an excess of lower-lobe tumors at a relatively low exposure level, independently of pulmonary fibrosis.

In plain English

This Finnish study related lung asbestos to lower-lobe lung cancer. The authors studied 90 lung cancer patients operated on at Helsinki University Hospital from 1988 to 1992. They combined work and smoking interviews, grading of lung scarring (fibrosis), and electron-microscope fiber counts. Anthophyllite was the most common fiber found. Lower-lobe tumors occurred in 20 of 32 patients (63%) with definite or probable work exposure, versus 14 of 57 (25%) possibly or unlikely exposed. Of 22 construction workers, 9 of the 11 (82%) with at least 15 years in the trade had lower-lobe tumors, versus 5 (45%) of the other 11. Adjusted for smoking and fibrosis, 3 million or more fibers per gram of dry lung gave an odds ratio of 9.0 (95% CI 2.3 to 34.6) for lower-lobe tumors, versus under 1 million. Fibrosis, smoking and fibers shorter than 3 micrometers did not explain location. The authors concluded that fiber count had an independent effect and suggested fiber size mattered more than asbestos type. They noted that the link at relatively low exposure and without asbestosis may be unique to Finnish patients.

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: Hospital-based study of surgically treated lung cancer patients. It combined occupational and smoking interviews, histological grading of fibrosis, and transmission electron microscopy counts of lung asbestos fibers. Tumor location was analyzed with logistic regression.
• Who was studied: 90 lung cancer patients (76 male, 14 female) operated on for a pulmonary tumor at Helsinki University Hospital, Finland, from August 1988 to January 1992. Patients whose surgery showed inflammatory lesions, probable secondary carcinomas or rare tumors were excluded.
• Exposure: Occupational asbestos exposure was classified from work history as definite, probable, possible or unlikely. 32 patients had definite or probable exposure, 24 of them in the construction trade. Lung fiber analysis found anthophyllite as the most prevalent type, along with crocidolite, chrysotile, tremolite and amosite. Fibers were counted by length (under 3, 3 to 5, and over 5 micrometers).
• Main results:
  • Lower-lobe tumors were found in 20 of 32 (63%) definitely or probably exposed patients and in 14 of 57 (25%) possibly or unlikely exposed patients (chi-square 10.94, p = 0.001).
  • Lower-lobe tumors were found in 16 of 27 patients (59%) with 2 million or more fibers per gram of lung tissue and in 18 of 62 (29%) with fewer (chi-square 6.06, p = 0.014).
  • The time-in-trade analysis covered 22 of the 24 construction workers; two were excluded. Of the 11 employed at least 15 years, 9 (82%) had a lower-lobe tumor, compared with 5 (45%) of those employed less than 15 years. The article does not state the denominator for the second group in that sentence. The figure of 11 is worked out as 22 minus 11, and it matches Table 2 and 5 of 11 being 45%.
  • In lower-lobe tumor patients, the mean fibrosis score was not elevated compared with upper-lobe tumor patients.
  • Adjusted for pack-years and fibrosis, a total fiber count of 3 million or more per gram gave an odds ratio of 9.0 for lower-lobe location (95% CI 2.3 to 34.6). Table 3 shows the reference level was fewer than 1 million fibers per gram. The middle category, 1 to under 3 million, had an adjusted odds ratio of 1.4 (CI 0.5 to 4.3).
  • Adjusted odds ratios for lower-lobe location were 22.1 (CI 3.9 to 125) for fibers 3 micrometers and longer and 14.6 (CI 2.4 to 83.4) for anthophyllite. For crocidolite, analyzed as 2 million or more versus fewer fibers, the odds ratio was 7.0 (CI 1.2 to 41.2).
  • Lower-lobe location was not explained by fibrosis score, pack-years smoked, or the number of fibers shorter than 3 micrometers.
• The authors' conclusion: The authors concluded that lung fiber count had an independent effect on tumor location after adjusting for smoking and fibrosis. They suggested that fiber size is more important than asbestos type in the lower-lobe tumors of asbestos-exposed patients.
• Limitations the authors state:
  • The effects of anthophyllite and crocidolite could not be fully separated, because construction workers especially were exposed to both.
  • Fibers may have broken down and cleared from the lung after exposure ended, so fiber levels during exposure may have been higher than those measured.
  • The association at a relatively low exposure level and without asbestosis may be unique to Finnish patients, whose lung fiber types differ from those in Britain and North America.

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Pulmonary Fibrosis, Occupational Exposure, Odds Ratio, Anthophyllite, Crocidolite, Fibrosis.

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