Quantitation of asbestos and asbestos-like fibers in human lung tissue by hot and wet ashing, and the significance of their presence for survival of lung carcinoma and mesothelioma patients

Our plain-English summary of Quantitation of asbestos and asbestos-like fibers in human lung tissue by hot and wet ashing, and the significance of their presence for survival of lung carcinoma and mesothelioma patients, by K. Kayser, C. Becker, N. Seeberg, et al (Lung Cancer, 1999).

The study

• Authors: K. Kayser, C. Becker, N. Seeberg, H.J. Gabius
• Journal: Lung Cancer
• Published: 1999;24(2):89-98
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Technical standardization on randomly chosen samples of tissue specimen is essential for the validity of interpretations derived from measurements on the presence of asbestos fibers in lung in combination with further features of the patients. Fixed non-tumorous lung tissue (2-3 g) of 150 patients after surgery for various lung diseases were either digested in 45 ml of 13% solution with sodium hypochlorite (NaClO; wet ashing) or heated in an oven at 600 degrees C for 15 min (hot ashing). After tissue disintegration asbestos and asbestos-like fibers were counted by visual inspection, and the fiber concentration in the lung parenchyma was computed. In addition, the patients' survival, and the occupational and social history were analyzed. As a result, the mean concentrations of fibers were found to be 55 f/g (fibers/gram, hot ashing) and 46 f/g (wet ashing). The difference is statistically not significant. Mesotheliomas contributed 49% (73 patients), non-small cell lung carcinomas 32% (59 patients) to the entire cohort. Eighteen patients had a non-malignant lung disease. Analysis of living habits revealed that 73 (49%) patients were heavy smokers, and 99 (66%) patients had a history of occupational asbestos exposure which lasted for 18 years on average. A statistically significant difference of the asbestos fiber concentration between the group with professional exposure and that without detectable asbestos exposure could be obtained in mesothelioma patients and non-malignant lung diseases only, and a tendency for elevated fiber presence was seen in non-small cell lung carcinoma patients. In tissue specimen of patients with non-malignant lung diseases the highest fiber concentration was measured (median 104 f/g) followed by mesothelioma patients (77 f/g), and lung carcinoma patients (62 f/g wet tissue). The difference in the fiber concentration between smokers and ex-smokers versus non-smokers was particularly high in patients with non-malignant lung diseases (103 f/g in smokers versus 33 f/g in non-smokers), still statistically significant in mesothelioma patients (100 f/g smokers versus 61 f/g non smokers), and negligible in lung carcinoma patients (58 f/g smokers versus 62 f/g non-smokers). Only 5/70 mesothelioma patients were not exposed to asbestos at work, and nearly half of the patients (36) were non-smokers. The median survival of mesothelioma patients was significantly shortened for patients with a high intrapulmonal fiber concentration greater than 70 f/g (35 weeks versus 60 weeks). This correlation was also true for lung carcinoma patients (110 weeks versus 230 weeks).

In plain English

This prospective study at the Thoraxklinik in Heidelberg, Germany, measured asbestos and asbestos-like fibers in disease-free lung tissue from 150 surgical patients treated between September 1995 and August 1996. Of these, 73 had mesothelioma, 59 had non-small cell lung carcinoma and 18 had non-malignant lung disease. Each tissue sample was split. One part was digested chemically (wet ashing) and the other was burned at 600°C (hot ashing), and fibers were counted under a light microscope. The two methods gave closely correlated results: a mean of 46 fibers per gram with wet ashing and 55 with hot ashing, a correlation of 0.97. Among mesothelioma and non-malignant disease patients, those with work-related asbestos exposure had higher median fiber counts (111 and 87 f/g) than those without reported exposure (33 and 47 f/g). In both cancer groups, more than 70 f/g went with shorter median survival: 35 versus 60 weeks for mesothelioma and 110 versus 230 weeks for lung carcinoma. The authors concluded that light-microscope counting after either method is feasible. They noted that workplace air levels were unknown.

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: Prospective study comparing two lung-tissue fiber counting methods (wet ashing and hot ashing) on the same samples, with analysis of exposure history, smoking and survival (Kaplan–Meier and multivariate analysis)
• Who was studied: 150 patients (141 men, 9 women) who had lung resection or decortication in the Department of Thoracic Surgery, Thoraxklinik, Heidelberg, from September 1, 1995 to August 31, 1996: 73 with mesothelioma, 59 with non-small cell lung carcinoma, 18 with non-malignant lung disease (14 emphysema, 3 lung infarctions, 1 hamartoma)
• Exposure: Occupational asbestos exposure taken from hospital files. The article's abstract reports 99 patients (66%) with such a history, lasting 18 years on average. Exposure was measured as the count of asbestos and asbestos-like fibers per gram of wet lung tissue by light microscopy. Fiber types were not separately identified.
• Main results:
  • Wet ashing gave a mean of 46 f/g and a median of 25 f/g. Hot ashing gave a mean of 55 f/g and a median of 31 f/g. The correlation between the two methods was 0.97.
  • Mesothelioma and non-malignant disease patients with work-related asbestos exposure had median fiber concentrations of 111 and 87 f/g. Those without reported exposure had 33 and 47 f/g. The difference was statistically significant (p less than 0.05).
  • In non-small cell lung carcinoma patients, only a tendency toward higher fiber counts was seen in those with work-related exposure.
  • Among patients with non-malignant lung disease, smokers had higher fiber concentrations than non-smokers (103 f/g versus 33 f/g, per the article's abstract). In lung carcinoma and mesothelioma patients, the discussion describes fiber concentration as only weakly associated with smoking.
  • In both the lung carcinoma and mesothelioma groups, a fiber concentration below 70 f/g was associated with more favorable survival.
  • Median survival for patients with more than 70 f/g versus lower counts was 35 versus 60 weeks in mesothelioma patients and 110 versus 230 weeks in lung carcinoma patients.
  • In multivariate survival analysis, fiber concentration ranked similarly to pN stage in lung carcinoma patients. In mesothelioma patients it ranked third, after weight loss and sex.
  • Smoking did not noticeably affect survival in mesothelioma or lung carcinoma patients.
• The authors' conclusion: The authors concluded that measuring asbestos and asbestos-like fibers by light microscopy after either thermal or chemical ashing is in principle feasible for estimating fiber contamination of lung tissue. They also concluded that fiber concentration was a parameter of prognostic relevance for survival.
• Limitations the authors state:
  • No information was available on workplace air contamination, so fiber-years could not be assessed.
  • Only tumor-free tissue was analyzed, so a locally higher fiber concentration at the tumor site would not be detected.
  • With hot ashing, some fibers may not withstand 600°C and may break.
  • With hot ashing, coated fibers (asbestos or ferruginous bodies) cannot be recognized.
  • No precise information was available on patients' use of cigarette filters, including asbestos filters.

Topics

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

Medical terms in this study, explained in our Lexicon: Carcinoma, Mesothelioma, Parenchyma, Habit, Asbestos Exposure, Median Survival.

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