Histologic types of lung cancer among uranium miners

Our plain-English summary of Histologic types of lung cancer among uranium miners, by G. Saccomanno, V. E. Archer, O. Auerbach, et al (1971).

The study

• Authors: G. Saccomanno, V. E. Archer, O. Auerbach, M. Kuschner, R. P. Saunders, M. G. Klein
• Published: Cancer, vol. 27, March 1971, pp. 515-523
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study, which is not about asbestos, examined lung cancer cell types in American uranium miners exposed to radiation from radon daughters in mine air. Three pathologists, working as a panel, classified 121 lung cancer cases among uranium miners and 138 cases among men who were not uranium miners. One miner with two separate primary cancers was counted as two cases. Controls came from 10 hospitals, which reviewed cases from January 1949 to July 1969. Miner cases came from these and other hospitals. Miners were matched with controls by age and cigarette smoking. Among the miners' lung cancers, the share that were small cell undifferentiated rose sharply with radiation exposure up to about 1500 Working Level Months (WLM) and then levelled off. The epidermoid share fell and then levelled off. In every exposure group except the lowest (40 to 200 WLM), miners differed significantly from their matched controls in small cell cancers. On average, 15.9 years passed between starting mining and the cancer. The authors concluded that cigarette smoking was a potent co-carcinogen but had little, if any, influence on cell type.

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: Pathology panel review of lung cancer cell types in uranium miners compared with controls matched for age and cigarette smoking
• Who was studied: 121 lung cancer cases among American uranium miners and 138 cancer cases among men who were not uranium miners. One miner with two different primary cancers was counted as two cases. Controls came from 10 hospitals served by one of the authors (Grand Junction, Colorado), where cases occurring between January 1949 and July 1969 were reviewed. Miner material came from these hospitals and from other hospitals.
• Exposure: Cumulative radiation exposure from radon daughters in uranium mine air, expressed in Working Level Months (WLM) and estimated from occupational histories. Miners were grouped as 40-200, 201-700, 701-1200, 1201-2500 and 2501-9700 WLM. No asbestos exposure was studied.
• Main results:
  • Among uranium miners' lung cancers, the relative frequency of small cell undifferentiated types (2A and 2B) increased sharply with radiation exposure up to about 1500 WLM and then reached a plateau. The 2B type reached a higher plateau than the 2A (oat cell) type.
  • Among uranium miners' lung cancers, the relative frequencies of epidermoid and 'other' cell types fell with increasing exposure to about 1500 WLM and then levelled off.
  • Within each WLM group, small cell undifferentiated cancers in miners were compared with those in their matched controls. The difference was statistically significant (95% confidence level) in all groups except 40-200 WLM. In that lowest group it was not statistically significant, though the authors described the trend as consistent.
  • Among uranium miners, an average of 15.9 years elapsed from the beginning of mining to the development of cancer.
  • Among uranium miners with small cell undifferentiated cancers, the mean induction-latent period was 9.4 years in the low exposure group (40-700 WLM). This was significantly different (p less than 0.005) from the 17.9 years in the comparable high exposure group (701+ WLM).
  • Of the 16 low-exposure miners with small cell undifferentiated cancers, 12 had done much other hard rock mining before uranium mining. Counted from first hard rock mining, their mean induction-latent period became 25.1 years instead of 9.4.
  • Among uranium miners, epidermoid cancers were significantly more frequent in older miners, with no consistent association with cigarette smoking.
  • Among uranium miners, heavy cigarette smoking was associated with a high frequency of the oat cell (2A) type among younger miners.
• The authors' conclusion: The authors concluded that among uranium miners, cigarette smoking is a potent co-carcinogen in lung cancer but exerts little, if any, influence on cell type, while age may exert a weak influence. They also found no evidence of selection bias in obtaining tissue.
• Limitations the authors state:
  • Slide readings could not be completely blind, because fibrosis and pigmentation in lung tissue often identified miners.
  • Individual radiation exposure (WLM) values relied on many estimates and are not precise.
  • There were too few control cases under 55 years of age to fully match younger miners, and matching became harder in the higher exposure groups.
  • Lower exposure groups likely contained more 'spontaneous' lung cancers, so the cell type shifts might partly reflect this 'dilution'.
  • Bone lead-210 measurements, considered more objective, were available for less than half the subjects, so occupational history estimates were used for all.
  • Some subgroups had small numbers.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer.

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